drm/radeon/kms: fix bad cast/shift in evergreen.c

Missing parens.

fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=30718

Reported-by: Dave Gilbert <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
Reviewed-by: Matt Turner <[email protected]>
Cc: [email protected]
Signed-off-by: Dave Airlie <[email protected]>
1 file changed