fix(el3-runtime): typecast operands to match data type

This corrects the MISRA violation C2012-10.3:
The value of an expression shall not be assigned to an object with a
narrower essential type or of a different essential type category.
Replaced usage of 'unsigned int' with 'size_t' to ensure type
consistency and prevent assignment to a narrower or different
essential type.

Change-Id: I79501e216a04753ebd005d64375357b9332440d9
Signed-off-by: Nithin G <nithing@amd.com>
Signed-off-by: Maheedhar Bollapalli <maheedharsai.bollapalli@amd.com>
diff --git a/include/lib/el3_runtime/cpu_data.h b/include/lib/el3_runtime/cpu_data.h
index 20a6c39..ba2f8d5 100644
--- a/include/lib/el3_runtime/cpu_data.h
+++ b/include/lib/el3_runtime/cpu_data.h
@@ -217,7 +217,7 @@
  * an access is not out-of-bounds. The function assumes security_state is
  * valid.
  */
-static inline context_pas_t get_cpu_context_index(uint32_t security_state)
+static inline context_pas_t get_cpu_context_index(size_t security_state)
 {
 	if (security_state == SECURE) {
 		return CPU_CONTEXT_SECURE;