msm: npu: Register cooling device after host init

While registering npu as a cooling device, thermal framework will
call registed APIs which causes "mutex used before initializing"
issue since mutex will be initialized in npu_host_init funciton.
This change is to register npu as cooling device after npu_host_init.

Change-Id: I99b9110b6bb871732addf96418fd3465145bc6f4
Signed-off-by: Jilai Wang <jilaiw@codeaurora.org>