ultrahdr: compress image reads outside bounds for non aligned widths

jpeg_write_raw_data() processes one MCU row per call, and thus one must
pass buffer of at least max_v_samp_factor * DCTSIZE scanlines. The
buffer must be large enough to hold the actual data plus padding
to DCT-block boundaries.

Bug: 284117683
Test: ./ultrahdr_enc_fuzzer

Change-Id: I993773817bf3805463bb21bb977624d6c2d45a0b