tty/serial: Migrate ip22zilog 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/ip22zilog.c

···
 #include <asm/sgi/hpc3.h>
 #include <asm/sgi/ip22.h>
 
-#if defined(CONFIG_SERIAL_IP22_ZILOG_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
-#define SUPPORT_SYSRQ
-#endif
-
 #include <linux/serial_core.h>
 
 #include "ip22zilog.h"
···
 
 static void __init ip22zilog_prepare(void)
 {
+	unsigned char sysrq_on = IS_ENABLED(CONFIG_SERIAL_IP22_ZILOG_CONSOLE);
 	struct uart_ip22zilog_port *up;
 	struct zilog_layout *rp;
 	int channel, chip;
···
 		up[(chip * 2) + 0].port.irq = zilog_irq;
 		up[(chip * 2) + 0].port.uartclk = ZS_CLOCK;
 		up[(chip * 2) + 0].port.fifosize = 1;
+		up[(chip * 2) + 0].port.has_sysrq = sysrq_on;
 		up[(chip * 2) + 0].port.ops = &ip22zilog_pops;
 		up[(chip * 2) + 0].port.type = PORT_IP22ZILOG;
 		up[(chip * 2) + 0].port.flags = 0;
···
 		up[(chip * 2) + 1].port.irq = zilog_irq;
 		up[(chip * 2) + 1].port.uartclk = ZS_CLOCK;
 		up[(chip * 2) + 1].port.fifosize = 1;
+		up[(chip * 2) + 1].port.has_sysrq = sysrq_on;
 		up[(chip * 2) + 1].port.ops = &ip22zilog_pops;
 		up[(chip * 2) + 1].port.type = PORT_IP22ZILOG;
 		up[(chip * 2) + 1].port.line = (chip * 2) + 1;