drm/vmwgfx: Fix a couple of sparse warnings and errors

Introduced with 3.14-rc1

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>

diff --cc drivers/gpu/drm/vmwgfx/vmwgfx_context.c
Simple merge

diff --cc drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
Simple merge

diff --cc drivers/gpu/drm/vmwgfx/vmwgfx_shader.c
Simple merge