GraphicBufferSource: ensure EOS buffer can be submitted

Sometimes, even mStopTimeUs is set by calling setStopTimeUs(), the EOS
buffer may still not be submitted, because fillCodecBuffer_l() may not
be called. So, remove this condition checking, and once if
submitEndOfInputStream_l() be called, mEndOfStremSent will be set to
true. So EOS buffer won't be send twice.

Bug: 2356695
Test: CTS test.
Change-Id: I5b69a9281f577e692eb2a471fe1998b0cb09ba45