esoc: mdm-4x: Add support for external mdm9x35

Mdm9x35 has more than one interface for communication.
The interface to be used is specified with the help of a gpio.

Change-Id: I09723e1c8a6e2e374a9b2166b655e8c4a349ca2d
Signed-off-by: Hanumant Singh <hanumant@codeaurora.org>