mali_kbase: probe: consolidate PCM and MGM deps

The mali_mgm and mali_pcm modules have been consolidated into
mali_pixel.

Bug: 183488552
Test: boot to Android home, check dmesg for mali-mgm and mali-pcm probe
Signed-off-by: Jesse Hall <jessehall@google.com>
Change-Id: I2a959e48260ce971cf2047ab4113ca5e2b05c08e