msm: rndis_ipa: Fix to incorrect state transition

Add a spinlock to protect the state transitions in rndis ipa
driver.

Change-Id: Ia5eab252d9a53e6a2f4db07912967a5f466982a6
Acked-by: Chaitanya Pratapa <cpratapa@qti.qualcomm.com>
Acked-by: Javid Mohammed <mjavid@qti.qualcomm.com>
Signed-off-by: Utkarsh Saxena <usaxena@codeaurora.org>
Signed-off-by: Sridhar Ancha <sancha@codeaurora.org>