serial: Fix upstat_t sparse warnings

Commit 299245a145,
serial: core: Privatize modem status enable flags, introduced
the upstat_t type and matching bit definitions. The purpose is to
produce sparse warnings if the wrong bit definitions are used
(by warning of implicit integer conversions).

Fix implicit conversion to integer return type from uart_cts_enabled()
and uart_dcd_enabled().

Fixes the following sparse warnings:
drivers/tty/serial/serial_core.c:63:30: warning: incorrect type in return expression (different base types)
drivers/tty/serial/serial_core.c:63:30:    expected int
drivers/tty/serial/serial_core.c:63:30:    got restricted upstat_t
include/linux/serial_core.h:364:30: warning: incorrect type in return expression (different base types)
include/linux/serial_core.h:364:30:    expected bool
include/linux/serial_core.h:364:30:    got restricted upstat_t
include/linux/serial_core.h:364:30: warning: incorrect type in return expression (different base types)
include/linux/serial_core.h:364:30:    expected bool
include/linux/serial_core.h:364:30:    got restricted upstat_t

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/serial_core.c

@@ -61,7 +61,7 @@ static void uart_port_shutdown(struct tty_port *port);
 
 static int uart_dcd_enabled(struct uart_port *uport)
 {
-	return uport->status & UPSTAT_DCD_ENABLE;
+	return !!(uport->status & UPSTAT_DCD_ENABLE);
 }
 
 /*

include/linux/serial_core.h

@@ -367,7 +367,7 @@ static inline int uart_tx_stopped(struct uart_port *port)
 
 static inline bool uart_cts_enabled(struct uart_port *uport)
 {
-	return uport->status & UPSTAT_CTS_ENABLE;
+	return !!(uport->status & UPSTAT_CTS_ENABLE);
 }
 
 /*