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: I9863df1e84a947fb04e29d214c1dec61ccc5ee72
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>