msm: watchdog: make watchdog a platform device

There are now several conditionals that control how the watchdog
behaves. We have described these in terms cpu_is and machine_is macros.
Instead, convert tunables to platform data so we can keep the driver
clean.

Additionally, since it is a platform device, we can now move the
suspending code to the suspend_noirq function, which leaves the watchdog
on for more of the suspend process.

Change-Id: If47b3abbeeaa40f4e6f0f5d301d0a28efa8d3535
Signed-off-by: Jeff Ohlstein <johlstei@codeaurora.org>