msm_bam_rmnet: Implement extended IOCTL's

Implement extended IOCTL's to query the ep id which gives
the mapping between the physical device and the BAM channel.

CRs-fixed: 660349
Change-Id: If78c8a96bbd88dbbceed77fb342d95bea53756af
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>