msm:npu: prevent fmax_pwrlvl to be used uninitialized

Initialize variable fmax_pwrlvl to prevent it being used
uninitialized.

Change-Id: Ie3f00292a74aa9d2ef57583979efa9d88f17b17a
Signed-off-by: Da Hoon Pyun <dpyun@codeaurora.org>