drm/vmwgfx: Replace the hw mutex with a hw spinlock

drm/vmwgfx: Replace the hw mutex with a hw spinlock

commit 496eb6fd2c3fd13f4b914e537598e5c86ce4f52a upstream.

Fixes a case where we call vmw_fifo_idle() from within a wait function with
task state !TASK_RUNNING, which is illegal.

In addition, make the locking fine-grained, so that it is performed once
for every read- and write operation. This is of course more costly, but we
don't perform much register access in the timing critical paths anyway. Instead
we have the extra benefit of being sure that we don't forget the hw lock around
register accesses. I think currently the kms code was quite buggy w r t this.

This fixes Red Hat Bugzilla Bug 1180796

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>