ARM: dts: Fix typo for omap4 mcasp rx path

As reported by Peter Ujfalusi <peter.ujfalusi@ti.com>, the rx path on macsp
is disabled and only tx is usable if the davinci-mcasp driver is updated for
it.
Reported-by: NPeter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>

arch/arm/boot/dts/omap4.dtsi

@@ -828,7 +828,7 @@
 
 			/*
 			 * Child device unsupported by davinci-mcasp. At least
-			 * TX path is disabled for omap4, and only DIT mode
+			 * RX path is disabled for omap4, and only DIT mode
 			 * works with no I2S. See also old Android kernel
 			 * omap-mcasp driver for more information.
 			 */