drm/radeon/r600: fix warnings in CS checker

drivers/gpu/drm/radeon/r600_cs.c: In function ‘r600_cs_track_check’:
drivers/gpu/drm/radeon/r600_cs.c:166: warning: ‘bpe’ may be used uninitialized in this function
drivers/gpu/drm/radeon/r600_cs.c:166: note: ‘bpe’ was declared here

drivers/gpu/drm/radeon/r600_cs.c: In function ‘r600_cs_parse’:
drivers/gpu/drm/radeon/r600_cs.c:938: warning: ‘bpe’ may be used uninitialized in this function
drivers/gpu/drm/radeon/r600_cs.c:938: note: ‘bpe’ was declared here

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>