spl: Use map_sysmem where appropriate

spl: Use map_sysmem where appropriate

All "physical" addresses in SPL must be converted to virtual addresses
before access in order for sandbox to work. Add some calls to map_sysmem in
appropriate places. We do not generally call unmap_sysmem, since we need
the image memory to still be mapped when we jump to the image. This doesn't
matter at the moment since unmap_sysmem is a no-op.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>