In CPHY, packet header and checksum is sent twice and SYNC is
sent in between two headers. So, increase packet overhead used
in clock calculation to 15 bytes. Packet Header: 8 bytes,
CRC: 4 bytes, SYNC: 2 bytes and dcs command: 1 byte.
Change-Id: I7a1160cbb57ba4f1faeb4b36a16c322e6069d58f
Signed-off-by: Ritesh Kumar <riteshk@codeaurora.org>