ANDROID: thermal: fix introduced kernelci warning

Using KBUILD_BUILD_USER=KernelCI ARCH=arm to build will introduce the
following warning
warning: ‘struct cpufreq_policy’declared inside parameter list will
not be visible outside of this definition or declaration
need to include cpufreq.h file.

Bug: 208166320

Fixes: fc827b34 ("ANDROID: thermal: Add vendor hooks for thermal")
Signed-off-by: Jeson Gao <jeson.gao@unisoc.com>
Change-Id: I1ec2f601ee7d8a4b793304c219c7735244d4da5c