uboot-imx

m68k: Change memsz to a signed char to avoid warning

There doesn't seem to be any reason for using uchar here, so change it
to char. This fixes a warning:

pointer targets in passing argument 1 of 'sprintf' differ in signedness

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Mike Frysinger <vapier@gentoo.org>