net: rmnet_data: Add support for MAPv4 data format

Add the MAPv4 ingress and data format handlers. MAPv4 requires the
checksum for uplink TCP and UDP packets to be 1's complemented
before passing the packet onto the physical netdevice.

This workaround is needed due to failures seen in hardware while
processing translated packets.

Change-Id: Ib79382fa7e8b2bd0c1adbe68b8de75f1602df10b
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>