h264_enc: Add test

The test accepts a raw YUV file, encoding parameters as input
and dumps encoded bitstream to a file.

To run the test, use following command
h264_enc_test <input yuv> <output file> <width> <height> <frame rate> <bitrate in kbps>

Bug: 17722566
Change-Id: I3711d455550ddfaa47003e10453ef1adc50f0d6f
Signed-off-by: Ashok Bhat <ashok.bhat@arm.com>