This change adds APIs to allocate and instanciate
multi instance gsi function driver using configFS.
Add an entry in kconfig to select diag driver for
configFS. This change fixes all compilation errors
caused by moving gsi driver from android.c to compile
independently.
Change-Id: I0ddb2ca155fd29c6d58fb561cc197f8efee3495a
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>