drm/vmwgfx: Get rid of the device-private suspended member

It was used to early block fbdev dirty processing. Replace it with an
unprotected check of the par->dirty.active field. While this might
race with the vmw_fb_off() function, we do a protected check later so
the race will at worst lead to grabbing and releasing a couple of locks.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>