msm: mdm: add mdm driver support for the sglte modem

The sglte QSC modem has its own firmware storage but powering
it on and reseting it is controlled by the msm. The same mdm
driver is used to support modems with their own flash and those
that are flashless.

Change-Id: I2f9a0e79a78cbe8eda1d887ce731386cbdf444e0
Signed-off-by: Joel King <joelking@codeaurora.org>