cpufreq: schedutil: Don't assume CPU of util update calls

Util updates for CPU A could be sent from CPU B. Don't make unnecessary
assumptions that are easy to avoid.

Change-Id: I9e60227bc1494661ec8d44657f0184c5abb4a6a9
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>