media: Only build when no variant is set

Change-Id: I4363e0c9163050932a52711d080b0957e1d5925c
Use actual kernel headers and display-caf paths if defined

Change-Id: I7338867f6eb4d88b33b610a2b2f93280ed6e71bc
QCMetaData: Add key for interlace

key for interlace set in metadata is being used for thumbnail mode.
If the key is set, two ETB are send to the decoder

Change-Id: I1e4e996f46f022916ab5f4f14ff2c111f04717c1