VT: ARTPWriter: StripStartcode() & SpsPpsParser() bug fix

[Problem]
    The striper can't pick a PPS unit from SPS-PPS-NAL concatenated byte stream.
    It picks PPS as PPS-NAL and this leads to infinite loop in sendAVCData()
[Solution]
    StripStartcode() is rolled back to as the first AOSP code.
    SpsPpsParser() do all parsing for SPS & PPS.
    The parser cuts the stream one-by-one by start-prefix-code(0x0 0x0 0x0 0x1)

Bug: 153702641
Bug: 165061754
Change-Id: I3453604784d5185c71673dd1344b1ea08a562651
Signed-off-by: Kim Sungyeon <sy85.kim@samsung.com>