C2SoftVpxEnc: Add support for encoding from a larger graphic block

Currently buffer dimensions are expected to be same as encode dimension.
Updated the checks to allow for encoding from larger graphic block

Bug: 158120386
Test: Encode 340x280 from a decoder surface with dimensions 384x288

Change-Id: I9eed491d3211b42cc4b9f7e42fb386240c745b15
1 file changed