msm: restart: initialize reboot code at early initcall time

It is possible for the kernel to panic on boot. Previously, in such a
case the kernel wouldn't enter download mode, which makes the issue that
much harder to debug. So, initialize the download mode magic early on.
The pmic interrupt part has to stay at late_initcall because it depends
on code that runs in setup_machine, which is an arch_initcall.

Change-Id: I4b6cee30cbb2b8cbcb288203e6f2cc8c17ed3a70
Signed-off-by: Jeff Ohlstein <johlstei@codeaurora.org>