tty/serial: Migrate pxa 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/20191213000657.931618-35-dima@arista.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/pxa.c

@@ -19,10 +19,6 @@
  */
 
 
-#if defined(CONFIG_SERIAL_PXA_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
-#define SUPPORT_SYSRQ
-#endif
-
 #include <linux/ioport.h>
 #include <linux/init.h>
 #include <linux/console.h>
@@ -879,6 +875,7 @@ static int serial_pxa_probe(struct platform_device *dev)
 	sport->port.dev = &dev->dev;
 	sport->port.flags = UPF_IOREMAP | UPF_BOOT_AUTOCONF;
 	sport->port.uartclk = clk_get_rate(sport->clk);
+	sport->port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_PXA_CONSOLE);
 
 	ret = serial_pxa_probe_dt(dev, sport);
 	if (ret > 0)