ARM: OMAP2+: UART: Fix compilation/sparse warnings

Fixes below compilation warning.

drivers/tty/serial/omap-serial.c: In function 'serial_omap_irq':
drivers/tty/serial/omap-serial.c:228:29: warning: 'ch' may be used uninitialized in this function [-Wuninitialized]

Fix below sparse warning.

drivers/tty/serial/omap-serial.c:392:52: warning: incorrect type in argument 2 (different signedness)
drivers/tty/serial/omap-serial.c:392:52:    expected int *status
drivers/tty/serial/omap-serial.c:392:52:    got unsigned int *<noident>

Reported-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Govindraj.R <govindraj.raja@ti.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de> (for drivers/tty changes)
Signed-off-by: Kevin Hilman <khilman@ti.com>

drivers/tty/serial/omap-serial.c

@@ -166,11 +166,12 @@ static void serial_omap_stop_rx(struct uart_port *port)
 	pm_runtime_put_autosuspend(&up->pdev->dev);
 }
 
-static inline void receive_chars(struct uart_omap_port *up, int *status)
+static inline void receive_chars(struct uart_omap_port *up,
+		unsigned int *status)
 {
 	struct tty_struct *tty = up->port.state->port.tty;
-	unsigned int flag;
-	unsigned char ch, lsr = *status;
+	unsigned int flag, lsr = *status;
+	unsigned char ch = 0;
 	int max_count = 256;
 
 	do {