cpufreq: schedutil: Give explicit hints to compiler

Make sure the compiler optimises away conditions that are always false
since commit b9131989 (cpufreq: schedutil: Don't jump to max frequency for RT tasks).

Change-Id: I7a108ff1a4ba09f2cb82ea8a82bd15967e724709
Signed-off-by: Alexander Winkowski <dereference23@outlook.com>