Fix bug with F4 clock settings, change HPRE to PPRE.

lib/stm32/f4/rcc.c

@@ -35,8 +35,8 @@ const clock_scale_t hse_8mhz_3v3[CLOCK_3V3_END] =
 		.pllp = 2,
 		.pllq = 5,
 		.hpre = RCC_CFGR_HPRE_DIV_NONE,
-		.ppre1 = RCC_CFGR_HPRE_DIV_4,
-		.ppre2 = RCC_CFGR_HPRE_DIV_2,
+		.ppre1 = RCC_CFGR_PPRE_DIV_4,
+		.ppre2 = RCC_CFGR_PPRE_DIV_2,
 		.power_save = 1,
 		.flash_config = FLASH_ICE | FLASH_DCE | FLASH_LATENCY_3WS,
 		.apb1_frequency = 30000000,
@@ -48,8 +48,8 @@ const clock_scale_t hse_8mhz_3v3[CLOCK_3V3_END] =
 		.pllp = 2,
 		.pllq = 7,
 		.hpre = RCC_CFGR_HPRE_DIV_NONE,
-		.ppre1 = RCC_CFGR_HPRE_DIV_4,
-		.ppre2 = RCC_CFGR_HPRE_DIV_2,
+		.ppre1 = RCC_CFGR_PPRE_DIV_4,
+		.ppre2 = RCC_CFGR_PPRE_DIV_2,
 		.flash_config = FLASH_ICE | FLASH_DCE | FLASH_LATENCY_5WS,
 		.apb1_frequency = 42000000,
 		.apb2_frequency = 84000000,