msm: rndis_ipa: fix state machine

RNDIS network interface driver has a state machine
that is used to control the driver operation.
This commit allows the driver to use the next-state
in order to decide what operation to do instead
of looking at the old state.

Change-Id: Icd96c3ab237c07301226f967476be46197fa5759
Signed-off-by: Talel Shenhar <tatias@codeaurora.org>