drm/cirrus: fix leaky driver load error handling

Before this patch, cirrus_device_init could have failed while
cirrus_mm_init succeeded and the driver would have reported overall
success on load. This patch causes cirrus_device_init to return on
the first error encountered.

BUG=None
TEST=None

Signed-off-by: Zach Reizner <zachr@chromium.org>
Change-Id: If84625fa96768eda8c1415beb0579465e07a27aa
Reviewed-on: https://chromium-review.googlesource.com/230525
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Merge branch 'chromeos-3.8' of https://chromium.googlesource.com/chromiumos/third_party/kernel into chromeos-3.8