fix: implicitly casts

Change macros to include an explicit cast to type size_t.
This was being hinted by clang-tidy of clang-14.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I4af78fcf5e5f5793584082b0b9cb61e0a9ab8f26
diff --git a/inc/hf/mm.h b/inc/hf/mm.h
index f76990a..e416103 100644
--- a/inc/hf/mm.h
+++ b/inc/hf/mm.h
@@ -10,6 +10,7 @@
 
 #include <stdalign.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 
 #include "hf/arch/mm.h"
@@ -21,7 +22,7 @@
 /* Keep macro alignment */
 /* clang-format off */
 
-#define PAGE_SIZE (1 << PAGE_BITS)
+#define PAGE_SIZE ((size_t)(1 << PAGE_BITS))
 #define MM_PTE_PER_PAGE (PAGE_SIZE / sizeof(pte_t))
 
 /* The following are arch-independent page mapping modes. */