[rbp/omxplayer] Fix bugs with jpeg parsing

I was finding GetCodingType to sometimes take 200ms for a single jpeg.
That was a mixture of the slow bit oriented parsing, and more significantly some bugs.
The SOF blocks skipped the wrong number of bytes, meaning we ended up parsing junk.
The M_TEM, M_DRI, M_SOI and M_EOI tags when seen (usually due to the junk) can only escape by slowly parsing until end of file.
Also, after a M_SOS, there is the variable sized jpeg block which we can't parse, so best to give up then, rather than misparsing the jpeg data