usb: dwc3: add glue layer dependencies

Glue layers for the DWC3 driver only make sense on specific platforms.
Add dependencies so that they are not built where they aren't needed.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: WingMan Kwok <w-kwok2@ti.com>
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/Kconfig

@@ -44,7 +44,7 @@ comment "Platform Glue Driver Support"
 
 config USB_DWC3_OMAP
 	tristate "Texas Instruments OMAP5 and similar Platforms"
-	depends on EXTCON
+	depends on EXTCON && (ARCH_OMAP2PLUS || COMPILE_TEST)
 	default USB_DWC3
 	help
 	  Some platforms from Texas Instruments like OMAP5, DRA7xxx and
@@ -54,6 +54,7 @@ config USB_DWC3_OMAP
 
 config USB_DWC3_EXYNOS
 	tristate "Samsung Exynos Platform"
+	depends on ARCH_EXYNOS || COMPILE_TEST
 	default USB_DWC3
 	help
 	  Recent Exynos5 SoCs ship with one DesignWare Core USB3 IP inside,
@@ -72,6 +73,7 @@ config USB_DWC3_PCI
 
 config USB_DWC3_KEYSTONE
 	tristate "Texas Instruments Keystone2 Platforms"
+	depends on ARCH_KEYSTONE || COMPILE_TEST
 	default USB_DWC3
 	help
 	  Support of USB2/3 functionality in TI Keystone2 platforms.