drm/r300: fix bug in r300 userspace hardware wait emission

This interface was originally designed wrong, confusing bit-fields and
integers, major brown paper bag going back many years...

But userspace only ever used 4 values so fix the interface for new
users and fix the implementation to deal with the 4 values userspace
has ever emitted (0x1, 0x2, 0x3, 0x6).

Signed-off-by: Dave Airlie <airlied@redhat.com>