Fixed data offset at parsing IPMP Descriptors

MPEG4Extractor::parseDrmSINF() miscalculated data offset in parsing
IPMP Descriptors. This commit makes it to take in 2 bytes which is
the size of IPMPS_Type field.

Change-Id: I42cbb6793af9d9b2f14dbfdd7a616096002793f9
1 file changed