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/bl31/interrupt_mgmt.c b/bl31/interrupt_mgmt.c
index 1a1cbc4..641d66a 100644
--- a/bl31/interrupt_mgmt.c
+++ b/bl31/interrupt_mgmt.c
@@ -78,7 +78,7 @@
  * routing model (expressed through the IRQ and FIQ bits) for a security state
  * which was stored through a call to 'set_routing_model()' earlier.
  ******************************************************************************/
-u_register_t get_scr_el3_from_routing_model(uint32_t security_state)
+u_register_t get_scr_el3_from_routing_model(size_t security_state)
 {
 	u_register_t scr_el3;