usb: typec: Fix setting of invalid value of opmode

Setting opmode to invalid values would lead to a
paging fault failure when there is an access to the
power_operation_mode.

Prevent this by checking the validity of the value
that the opmode is being set.

Change-Id: I9ada1ad4aeeca08d3072a5738f5fa48537a2cecf
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>