rmnet_bam: Free netdevice resources if init fails

In the init routine, after the netdevice is allocated,
there are failure cases, where the netdevice was not
being unregistered and free'd. This patch handles all the
failure cases in the init routine and does the necessary
clean up.

CRs-Fixed: 490419
Change-Id: I71b2318e61dffa1e2dca0e835ec6d964679b2639
Signed-off-by: Harout Hedeshian <harouth@codeaurora.org>