SiS DRM: fix the memory allocator if the SIS FB is built as a module

SiS DRM: fix the memory allocator if the SIS FB is built as a module

Fix the SIS DRM memory allocator if the SIS FB built as a module.  The SIS DRM
code initialises the mm allocation hooks, but _only_ if the SIS FB is not
built as a module because it depends on CONFIG_FB_SIS, and that's unset if the
SIS FB is not built in.  It must check CONFIG_FB_SIS_MODULE as well.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>