staging: Hook the DWC2 driver into the build system

Add the DWC2 Kconfig and Makefile, and modify the staging Kconfig and
Makefile to include them

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/staging/Kconfig b/drivers/staging/Kconfig
index daeeec1..95f9110 100644
--- a/drivers/staging/Kconfig
+++ b/drivers/staging/Kconfig
@@ -142,4 +142,6 @@
 
 source "drivers/staging/netlogic/Kconfig"
 
+source "drivers/staging/dwc2/Kconfig"
+
 endif # STAGING