msm: vidc: Omit check for msm_fw_low_power_mode in setting power control

A minor code clean up.  msm_fw_low_power_mode is already being passed in
as an argument into venus_hfi_sys_set_power_control() as the enable
flag.

Change-Id: Ibe0517f31f815d7a8481664bb7781ca2461afa6c
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>