Adding Error Check for f_code Parameters

In MPEG1, the valid range for the forward and backward f_code parameters
is [1, 7]. Adding a check to enforce this. Without the check, the value
could be 0. We read (f_code - 1) bits from the stream and reading a
negative number of bits from the stream is undefined.

Bug: 64550583
Test: monitored temp ALOGD() output
Change-Id: Ia452cd43a28e9d566401f515947164635361782f