mtd: sh_flctl: Use memcpy() instead of using a loop

Elements have been copied "manually" in a loop. Better use memcpy().

Signed-off-by: Bastian Hecht <hechtb@gmail.com>
Reviewed-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>