devfreq: Compilation error fix for 32-bit kernel

This fixes below compilation error for 32bit kernel build.
Comparison of distinct pointer types - 'unsigned long' with
'unsigned long long'. Change is to use uint64_t to fix this.

Change-Id: I5c76433854eff81c850fb44381e418f2bdc1a8c7
Signed-off-by: Lijuan Gao <lijuang@codeaurora.org>