msm: mdm: add device tree support to the mdm driver

Device tree support for the mdm driver is needed for targets
that support device tree and have attached external modems.
This involves creating a platform data structure from
resources in a device tree node for each external modem. As
a result of this, some new functions have been added and the
call signature of some existing functions have changed.

Change-Id: I9f0a4a98aaeefd314510b1aec73e066ce9d5e014
Signed-off-by: Joel King <joelking@codeaurora.org>