net: rmnet_data: Move MAP header definition to UAPI

Expose the MAP header to the rest of the kernel and user space. Useful for
making various parts of the kernel MAP aware. Keeping consistency with
other networking procols by exposing protocol headers to user space with
a header file in UAPI.

CRs-Fixed: 681280
Change-Id: Ic7f414f926f68531418725f971ab2b44459f5ea1
Signed-off-by: Harout Hedeshian <harouth@codeaurora.org>