Allow fd access between mediacodec and bufferhubd

bufferhubd should be able to use sync fence fd from mediacodec; and
mediacodec should be able to use a gralloc buffer fd from the bufferhubd.

Bug: 32213311
Test: Ran exoplayer_demo and verify mediacodec can plumb buffer through
bufferhub.

Change-Id: Id175827c56c33890ecce33865b0b1167d872fc56