ultrahdr: make decodeJPEGR behaviour synonymous with getJPEGRInfo

For a given image, if getJPEGRInfo returns with error, then its best
to ensure decodeJPEGR exhibits identical behaviour.

Currently decodeJPEGR is decoding primary image directly. If
getJPEGRInfo fails with error, then it is not possible for client to
allocate space for dest for decodeJPEGR. Ignoring the error, if the
client allocates some space and calls decodeJPEGR, its possible
we see SIGSEGV issues.

Bug: 286208319
Test: ./ultrahdr_dec_fuzzer

Change-Id: I04f70a6bf895efce0c0f0ec62ca0fcda2f78acbc
Merged-In: I04f70a6bf895efce0c0f0ec62ca0fcda2f78acbc
(cherry picked from commit cdc0f1fa)