serial: add UART_CAP_EFR and UART_CAP_SLEEP flags to 16C950 UARTs definition

Adding UART_CAP_EFR and UART_CAP_SLEEP flags will enable sleep mode
and automatic CTS flow control for 16C950 UARTs. It will also avoid
capabilities detection warning like this:

"ttyS0: detected caps 00000700 should be 00000100"
Signed-off-by: NYegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/serial/8250.c

@@ -241,7 +241,7 @@ static const struct serial8250_config uart_config[] = {
 		.fifo_size	= 128,
 		.tx_loadsz	= 128,
 		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
-		.flags		= UART_CAP_FIFO,
+		.flags		= UART_CAP_FIFO | UART_CAP_EFR | UART_CAP_SLEEP,
 	},
 	[PORT_16654] = {
 		.name		= "ST16654",