ARM: dts: atlas7: Use generic uart-has-rtscts DT property

As of commit 7f60830a ("serial: sirf: Use generic
uart-has-rtscts DT property property"), the SiRF UART driver recognizes
the generic "uart-has-rtscts" DT property, deprecating the
vendor-specific "sirf,uart-has-rtscts" DT property. Hence replace the
latter by the former in all DTS files.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>

arch/arm/boot/dts/atlas7-evb.dts

@@ -73,7 +73,7 @@
 		btm {
 			uart6: uart@11000000 {
 				status = "okay";
-				sirf,uart-has-rtscts;
+				uart-has-rtscts;
 			};
 		};