msm: kgsl: Add missing braces in opp_notify

Add missing braces to for loop to make sure both
max_level and min_level gets updated properly.

Change-Id: Ic1135c2e740787b8f9066a14467cb670c772d1bd
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>
Signed-off-by: Urvashi Agrawal <urvaagra@codeaurora.org>