doc: stm32l0: rcc: add groups requested by existing docs

And cleanse the arguments to all match the docs.

include/libopencm3/stm32/l0/rcc.h

@@ -142,14 +142,17 @@
 #define RCC_CFGR_MCO_SHIFT			24
 #define RCC_CFGR_MCO_MASK			0xf
 
-/* PLL Output division selection */
+/** @defgroup rcc_cfgr_pdf PLLDIV PLL division factor
+ @{*/
 #define RCC_CFGR_PLLDIV_DIV2	0x1
 #define RCC_CFGR_PLLDIV_DIV3	0x2
 #define RCC_CFGR_PLLDIV_DIV4	0x3
+/**@}*/
 #define RCC_CFGR_PLLDIV_SHIFT	22
 #define RCC_CFGR_PLLDIV_MASK	0x3
 
-/* PLLMUL: PLL multiplication factor */
+/** @defgroup rcc_cfgr_pmf PLLMUL PLL multiplication factor
+ @{*/
 #define RCC_CFGR_PLLMUL_MUL3		0x0
 #define RCC_CFGR_PLLMUL_MUL4		0x1
 #define RCC_CFGR_PLLMUL_MUL6		0x2
@@ -159,6 +162,7 @@
 #define RCC_CFGR_PLLMUL_MUL24		0x6
 #define RCC_CFGR_PLLMUL_MUL32		0x7
 #define RCC_CFGR_PLLMUL_MUL48		0x8
+/**@}*/
 #define RCC_CFGR_PLLMUL_SHIFT		18
 #define RCC_CFGR_PLLMUL_MASK		0xf
 

lib/stm32/l0/rcc.c

@@ -309,7 +309,7 @@ void rcc_set_sysclk_source(enum rcc_osc osc)
  *
  * @note This only has effect when the PLL is disabled.
  *
- * @param[in] mul Unsigned int32. PLL multiplication factor @ref rcc_cfgr_pmf
+ * @param[in] factor PLL multiplication factor @ref rcc_cfgr_pmf
  */
 
 void rcc_set_pll_multiplier(uint32_t factor)
@@ -325,7 +325,7 @@ void rcc_set_pll_multiplier(uint32_t factor)
  *
  * @note This only has effect when the PLL is disabled.
  *
- * @param[in] mul Unsigned int32. PLL multiplication factor @ref rcc_cfgr_pdf
+ * @param[in] factor PLL multiplication factor @ref rcc_cfgr_pdf
  */
 
 void rcc_set_pll_divider(uint32_t factor)
@@ -353,7 +353,7 @@ void rcc_set_pll_source(uint32_t pllsrc)
  *
  * @note The APB1 clock frequency must not exceed 32MHz.
  *
- * @param[in] ppre1 Unsigned int32. APB prescale factor @ref rcc_cfgr_apb1pre
+ * @param[in] ppre APB prescale factor @ref rcc_cfgr_apb1pre
  */
 
 void rcc_set_ppre1(uint32_t ppre)
@@ -368,7 +368,7 @@ void rcc_set_ppre1(uint32_t ppre)
  *
  * @note The APB2 clock frequency must not exceed 32MHz.
  *
- * @param[in] ppre1 Unsigned int32. APB prescale factor @ref rcc_cfgr_apb2pre
+ * @param[in] ppre APB prescale factor @ref rcc_cfgr_apb2pre
  */
 
 void rcc_set_ppre2(uint32_t ppre)
@@ -393,7 +393,7 @@ void rcc_set_hpre(uint32_t hpre)
 /*---------------------------------------------------------------------------*/
 /** @brief Set the range of the MSI oscillator
 *
- * @param range desired range @ref rcc_icscr_msirange
+ * @param msi_range desired range @ref rcc_icscr_msirange
  */
 void rcc_set_msi_range(uint32_t msi_range)
 {
@@ -448,8 +448,8 @@ void rcc_set_usart2_sel(uint32_t usart2_sel)
 
 /*---------------------------------------------------------------------------*/
 /** @brief Set the peripheral clock source
-*
- * @param sel periphral clock source
+ * @param periph peripheral of desire, eg XXX_BASE
+ * @param sel peripheral clock source
  */
 void rcc_set_peripheral_clk_sel(uint32_t periph, uint32_t sel)
 {