lib: fix switch statements to comply with MISRA rules

Ensure (where possible) that switch statements in lib comply with MISRA
rules 16.1 - 16.7.

Change-Id: I52bc896fb7094d2b7569285686ee89f39f1ddd84
Signed-off-by: Jonathan Wright <jonathan.wright@arm.com>
diff --git a/include/lib/pmf/pmf.h b/include/lib/pmf/pmf.h
index a3d3226..2320760 100644
--- a/include/lib/pmf/pmf.h
+++ b/include/lib/pmf/pmf.h
@@ -37,8 +37,8 @@
 /*
  * Defines for PMF SMC function ids.
  */
-#define PMF_SMC_GET_TIMESTAMP_32	0x82000010
-#define PMF_SMC_GET_TIMESTAMP_64	0xC2000010
+#define PMF_SMC_GET_TIMESTAMP_32	0x82000010u
+#define PMF_SMC_GET_TIMESTAMP_64	0xC2000010u
 #define PMF_NUM_SMC_CALLS		2
 
 /*