xtensa: xtfpga: set ethoc clock frequency

Connect xtfpga board ethernet MAC to the clock in the DTS. Set up MAC
base frequency in the platform data in case of build w/o CONFIG_OF.

Signed-off-by: Max Filippov <[e-mail]>

arch/xtensa/boot/dts/xtfpga.dtsi

···
 		reg = <0xfd030000 0x4000 0xfd800000 0x4000>;
 		interrupts = <1 1>; /* external irq 1 */
 		local-mac-address = [00 50 c2 13 6f 00];
+		clocks = <&osc>;
 	};
 };

arch/xtensa/platforms/xtfpga/setup.c

···
 	 * knows whether they set it correctly on the DIP switches.
 	 */
 	pr_info("XTFPGA: Ethernet MAC %pM\n", ethoc_pdata.hwaddr);
+	ethoc_pdata.eth_clkfreq = *(long *)XTFPGA_CLKFRQ_VADDR;
 
 	return 0;
 }