arm: socfpga: arria5-socdk: Probe DWC2 UDC from OF instead of hard-coded data

This patch adds the necessary OF alias for the UDC node, which let's
the code locate the DWC2 UDC base address in OF instead of hard-coding
it into the U-Boot binary. The code is adjusted to use the address from
OF instead of the hard-coded one. Finally, the hard-coded address is
removed and USB DM support is enabled.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
Cc: Lukasz Majewski <l.majewski@majess.pl>
Cc: Lukasz Majewski <l.majewski@samsung.com>
diff --git a/arch/arm/dts/socfpga_arria5_socdk.dts b/arch/arm/dts/socfpga_arria5_socdk.dts
index 7d1836e..5933a40 100644
--- a/arch/arm/dts/socfpga_arria5_socdk.dts
+++ b/arch/arm/dts/socfpga_arria5_socdk.dts
@@ -25,6 +25,7 @@
 		 * to be added to the gmac1 device tree blob.
 		 */
 		ethernet0 = &gmac1;
+		udc0 = &usb1;
 	};
 
 	regulator_3_3v: 3-3-v-regulator {