ARC: [nsimosci] Change .dts to use generic 8250 UART

The Synopsys APB DW UART has a couple of special features that are not
in the System C model. In 3.8, the 8250_dw driver didn't really use these
features, but from 3.9 onwards, the 8250_dw driver has become incompatible
with our model.
Signed-off-by: Mischa Jonker <mjonker@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: <stable@vger.kernel.org>   #3.10, 3.12, 3.13, 3.14
Cc: Francois Bedard <Francois.Bedard@synopsys.com>

arch/arc/boot/dts/nsimosci.dts

@@ -11,7 +11,7 @@
 
 / {
 	compatible = "snps,nsimosci";
-	clock-frequency = <80000000>;	/* 80 MHZ */
+	clock-frequency = <20000000>;	/* 20 MHZ */
 	#address-cells = <1>;
 	#size-cells = <1>;
 	interrupt-parent = <&intc>;
@@ -44,15 +44,14 @@ intc: interrupt-controller {
 		};
 
 		uart0: serial@c0000000 {
-			compatible = "snps,dw-apb-uart";
+			compatible = "ns8250";
 			reg = <0xc0000000 0x2000>;
 			interrupts = <11>;
-			#clock-frequency = <80000000>;
 			clock-frequency = <3686400>;
 			baud = <115200>;
 			reg-shift = <2>;
 			reg-io-width = <4>;
-			status = "okay";
+			no-loopback-test = <1>;
 		};
 
 		pgu0: pgu@c9000000 {