Add GENMASK macros

Import GENMASK_32 and GENMASK_64 macros from optee-os (permissive license).
And default GENMASK is set to GENMASK_32 for AARCH32,
and to GENMASK_64 for 64bit arch.

fixes arm-software/tf-issues#596

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Nicolas Le Bayon <nicolas.le.bayon@st.com>

include/lib/utils_def.h

@@ -18,6 +18,23 @@
 
 #define BIT(nr)				(ULL(1) << (nr))
 
+/*
+ * Create a contiguous bitmask starting at bit position @l and ending at
+ * position @h. For example
+ * GENMASK_64(39, 21) gives us the 64bit vector 0x000000ffffe00000.
+ */
+#define GENMASK_32(h, l) \
+	(((~UINT32_C(0)) << (l)) & (~UINT32_C(0) >> (32 - 1 - (h))))
+
+#define GENMASK_64(h, l) \
+	(((~UINT64_C(0)) << (l)) & (~UINT64_C(0) >> (64 - 1 - (h))))
+
+#ifdef AARCH32
+#define GENMASK				GENMASK_32
+#else
+#define GENMASK				GENMASK_64
+#endif
+
 /*
  * This variant of div_round_up can be used in macro definition but should not
  * be used in C code as the `div` parameter is evaluated twice.