msm: pil: Migrate to pil_boot()/pil_shutdown() API

Migrate to the new API so that we can remove the PIL bus layer
and pil_force_boot()/pil_force_shutdown() in a future patch.

The basic conversion is to replace msm_pil_register() with
pil_desc_init(), msm_pil_unregister() with pil_desc_release(),
pil_force_boot() with pil_boot() and pil_force_shutdown() with
pil_shutdown().

Change-Id: Ib3a3b80b33fae3bbeb50c4b896165dc1fef36ce4
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>