[CPUFREQ] Fix _OSC UUID in pcc-cpufreq

UUID needs to be written out the way it is described in
Sec 18.5.124 of ACPI 4.0a Specification.

Platform firmware's use of this UUID/_OSC is optional, which is
why we didn't notice this bug earlier.

Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
Signed-off-by: Dave Jones <davej@redhat.com>
Cc: stable@kernel.org