x86: Tidy up error handling in mrccache_save()

x86: Tidy up error handling in mrccache_save()

This function is a bit confusing at present due to the error handling.
Update it to remove the goto, returning errors as they happen.

While we are here, use hex for the data size since this is the norm in
U-Boot.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>