test: add some jpeg encode tests

test: add some jpeg encode tests

Add JPEG encode tests that encode raw I420 and NV12 data
at quality 100 and then decodes them to verify proper
encoding.

Currently, the 7680x4320 I420 test fails because ~40-60
Y-values (i.e. plane 0) in each line from the decoded
bitstream are off by more than 2 of the original raw
I420 values.  It is not clear why only this resolution
exhibits this problem.

v2: don't create any input data in test fixture if
jpeg encoding is not supported.

Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
Reviewed-by: Zhao Yakui <yakui.zhao@intel.com>