OMAP/serial: Revert bad fix of Rx FIFO threshold granularity

Partially reverts 1776fd059c
that introduced regression reported by Paul Walmsley.

This commit restores setting granularity in SCR register
and adds note about comments below being inconsistent with
actual code.

Signed-off-by: Alexey Pelykh <alexey.pelykh@gmail.com>
Tested-by: Paul Walmsley <paul@pwsan.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/omap-serial.c

@@ -886,6 +886,17 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
 	serial_out(up, UART_MCR, up->mcr | UART_MCR_TCRTLR);
 	/* FIFO ENABLE, DMA MODE */
 
+	up->scr |= OMAP_UART_SCR_RX_TRIG_GRANU1_MASK;
+	/*
+	 * NOTE: Setting OMAP_UART_SCR_RX_TRIG_GRANU1_MASK
+	 * sets Enables the granularity of 1 for TRIGGER RX
+	 * level. Along with setting RX FIFO trigger level
+	 * to 1 (as noted below, 16 characters) and TLR[3:0]
+	 * to zero this will result RX FIFO threshold level
+	 * to 1 character, instead of 16 as noted in comment
+	 * below.
+	 */
+
 	/* Set receive FIFO threshold to 16 characters and
 	 * transmit FIFO threshold to 16 spaces
 	 */