Print warning when upgrading bitdepth
Print warning when upgrading bitdepth

Matches behavior for profile upgrading

BUG=aomedia:2147

Change-Id: I28762c3ba6aea35f91648437ea630fff047ff60a

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom