qcacld-3.0: Fix variable type in sch_gen_timing_advert_frame

Currently inside the function sch_gen_timing_advert_frame, the variable
type used to hold the return value of populate_dot11f_timing_advert_frame,
is incorrect. So, fix it with correct variable type.

Change-Id: I592c1b3c291b4c9dce2cbe731021cf512cb598f2
CRs-Fixed: 3243257
1 file changed