dts: dra7: add spi alias for qspi

add spi alias for qspi so that spi probes the device and driver
successfully.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagan Teki <jteki@openedev.com>

arch/arm/dts/dra7.dtsi

@@ -41,6 +41,7 @@
 		ethernet1 = &cpsw_emac1;
 		d_can0 = &dcan1;
 		d_can1 = &dcan2;
+		spi0 = &qspi;
 	};
 
 	timer {