msm: pil-modem: Combine SSR and PIL drivers

Combine both drivers into one so that we can merge the PIL and
SSR frameworks. We drop the modem_restart workqueue code because
it is debug code that is no longer necessary.

Change-Id: I5730ff06ee7c0f67b56263c0df9344b229441da2
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>