tty/serial: Migrate msm_serial 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.

Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: linux-arm-msm@vger.kernel.org
Signed-off-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20191213000657.931618-26-dima@arista.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/msm_serial.c

@@ -7,10 +7,6 @@
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  */
 
-#if defined(CONFIG_SERIAL_MSM_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
-# define SUPPORT_SYSRQ
-#endif
-
 #include <linux/kernel.h>
 #include <linux/atomic.h>
 #include <linux/dma-mapping.h>
@@ -1801,6 +1797,7 @@ static int msm_serial_probe(struct platform_device *pdev)
 	if (unlikely(irq < 0))
 		return -ENXIO;
 	port->irq = irq;
+	port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_MSM_CONSOLE);
 
 	platform_set_drvdata(pdev, port);