usb: dwc3: select CONFIG_REGMAP_MMIO

After many randconfig builds, one configuration caused a link
error with dwc3-meson-g12a lacking the regmap-mmio code:

drivers/usb/dwc3/dwc3-meson-g12a.o: In function `dwc3_meson_g12a_probe':
dwc3-meson-g12a.c:(.text+0x9f): undefined reference to `__devm_regmap_init_mmio_clk'

Add the select statement that we have for all other users
of that dependency.

Fixes: c9999337 ("usb: dwc3: Add Amlogic G12A DWC3 glue")
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/Kconfig

@@ -102,6 +102,7 @@ config USB_DWC3_MESON_G12A
        depends on ARCH_MESON || COMPILE_TEST
        default USB_DWC3
        select USB_ROLE_SWITCH
+	select REGMAP_MMIO
        help
          Support USB2/3 functionality in Amlogic G12A platforms.
 	 Say 'Y' or 'M' if you have one such device.