ARM: 9468/1: fix memset64() on big-endian

ARM: 9468/1: fix memset64() on big-endian

On big-endian systems the 32-bit low and high halves need to be swapped
for the underlying assembly implementation to work correctly.

Fixes: fd1d362600e2 ("ARM: implement memset32 & memset64")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>