msm: mdm: add a timer to check that mdm2ap_status gpio goes high

The timer is started after flashless boot is completed but before
the mdm2ap_status gpio is pulled high by the external modem. If
the mdm2ap_status gpio does not go high within a period of time
a subsystem restart is initiated.

CRs-Fixed: 358868
Change-Id: Iba410a38a0b21fea8425c7e5a47bfec5f3a203e7
Signed-off-by: Joel King <joelking@codeaurora.org>