tty/serial: Migrate mpc52xx_uart to use has_sysrq

The SUPPORT_SYSRQ ifdeffery is not nice as:
- May create misunderstanding about sizeof(struct uart_port) between
  different objects
- Prevents moving functions from serial_core.h
- Reduces readability (well, it's ifdeffery - it's hard to follow)

In order to remove SUPPORT_SYSRQ, has_sysrq variable has been added.
Initialise it in driver's probe and remove ifdeffery.
Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20191213000657.931618-24-dima@arista.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/mpc52xx_uart.c

@@ -44,10 +44,6 @@
 #include <asm/mpc52xx.h>
 #include <asm/mpc52xx_psc.h>
 
-#if defined(CONFIG_SERIAL_MPC52xx_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
-#define SUPPORT_SYSRQ
-#endif
-
 #include <linux/serial_core.h>
 
 
@@ -1382,12 +1378,10 @@ mpc52xx_uart_int_rx_chars(struct uart_port *port)
 		ch = psc_ops->read_char(port);
 
 		/* Handle sysreq char */
-#ifdef SUPPORT_SYSRQ
 		if (uart_handle_sysrq_char(port, ch)) {
 			port->sysrq = 0;
 			continue;
 		}
-#endif
 
 		/* Store it */
 
@@ -1770,6 +1764,7 @@ static int mpc52xx_uart_of_probe(struct platform_device *op)
 	spin_lock_init(&port->lock);
 	port->uartclk = uartclk;
 	port->fifosize	= 512;
+	port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_MPC52xx_CONSOLE);
 	port->iotype	= UPIO_MEM;
 	port->flags	= UPF_BOOT_AUTOCONF |
 			  (uart_console(port) ? 0 : UPF_IOREMAP);