uart: 16550: Fix getc

tbz check for RDR status is to check for a bit being zero.
Unfortunately, we are using a mask rather than the bit position.

Further as per http://www.ti.com/lit/ds/symlink/pc16550d.pdf (page 17),
LSR register bit 0 is Data ready status (RDR), not bit position 2.

Update the same to match the specification.

Reported-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
diff --git a/include/drivers/ti/uart/uart_16550.h b/include/drivers/ti/uart/uart_16550.h
index 2c814ef..773e2f1 100644
--- a/include/drivers/ti/uart/uart_16550.h
+++ b/include/drivers/ti/uart/uart_16550.h
@@ -88,6 +88,7 @@
 #define UARTLSR_FERR		(1 << 3)	/* Framing Error */
 #define UARTLSR_PERR		(1 << 3)	/* Parity Error */
 #define UARTLSR_OVRF		(1 << 2)	/* Rx Overrun Error */
-#define UARTLSR_RDR		(1 << 2)	/* Rx Data Ready */
+#define UARTLSR_RDR_BIT		(0)		/* Rx Data Ready Bit */
+#define UARTLSR_RDR		(1 << UARTLSR_RDR_BIT)	/* Rx Data Ready */
 
 #endif	/* __UART_16550_H__ */