AARCH64 gcc error with const qualifiers

aarch64-linux-gnu-gcc on Debian/Sid fails lib compilation with:
lib/aarch64/initplat.c:44:35: error: initialization discards
‘const’ qualifier from pointer target type
[-Werror=discarded-qualifiers].  This patch fixes it.

Signed-off-by: Pete Batard <pete@akeo.ie>
Signed-off-by: Nigel Croxon <noxorc@users.sf.net>

lib/aarch64/initplat.c

@@ -41,7 +41,8 @@ void *memset(void *s, int c, __SIZE_TYPE__ n)
 
 void *memcpy(void *dest, const void *src, __SIZE_TYPE__ n)
 {
-    unsigned char *p = dest, *q = src;
+    const unsigned char *q = src;
+    unsigned char *p = dest;
 
     while (n--)
         *p++ = *q++;