tty/serial: Migrate sccnxp 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 <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/sccnxp.c

···
  *  Based on sc26xx.c, by Thomas Bogendörfer ([e-mail])
  */
 
-#if defined(CONFIG_SERIAL_SCCNXP_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
-#define SUPPORT_SYSRQ
-#endif
-
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/err.h>
···
 		s->port[i].regshift	= s->pdata.reg_shift;
 		s->port[i].uartclk	= uartclk;
 		s->port[i].ops		= &sccnxp_ops;
+		s->port[i].has_sysrq = IS_ENABLED(CONFIG_SERIAL_SCCNXP_CONSOLE);
 		uart_add_one_port(&s->uart, &s->port[i]);
 		/* Set direction to input */
 		if (s->chip->flags & SCCNXP_HAVE_IO)