fix(rmm): fix MISRA C:2012 Rule 8.3 violations

Fixes Function Declaration to use the same name and type
as the definition.

Signed-off-by: AlexeiFedorov <Alexei.Fedorov@arm.com>
Change-Id: I4f83457ef62779cc93967f0526fa4aaeb68b14fb
diff --git a/lib/realm/include/buffer.h b/lib/realm/include/buffer.h
index 7cb0a39..dc716de 100644
--- a/lib/realm/include/buffer.h
+++ b/lib/realm/include/buffer.h
@@ -43,12 +43,12 @@
 void buffer_unmap(void *buf);
 
 bool ns_buffer_read(enum buffer_slot slot,
-		    struct granule *granule,
+		    struct granule *ns_gr,
 		    unsigned int offset,
 		    unsigned int size,
 		    void *dest);
 bool ns_buffer_write(enum buffer_slot slot,
-		     struct granule *granule,
+		     struct granule *ns_gr,
 		     unsigned int offset,
 		     unsigned int size,
 		     void *src);