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>