do not send max pts gap to full-frame image encoders

Image encoders don't use pts for rate control and should take
backward pts just fine. Also OMXNodeInstance timestamp restore
assume one input buffer maps to one output.

bug: 141169323
test: vendor testing of Camera CTS
ReprocessCaptureTest-testMixedBurstReprocessing

Change-Id: I17db3b5fb363878c9daf33c914fd2e1e88029cfe