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

drivers/tty/serial/pch_uart.c

···
 /*
  *Copyright (C) 2011 LAPIS Semiconductor Co., Ltd.
  */
-#if defined(CONFIG_SERIAL_PCH_UART_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
-#define SUPPORT_SYSRQ
-#endif
 #include <linux/kernel.h>
 #include <linux/serial_reg.h>
 #include <linux/slab.h>
···
 			if (uart_handle_break(port))
 				continue;
 		}
-#ifdef SUPPORT_SYSRQ
 		if (port->sysrq) {
 			if (uart_handle_sysrq_char(port, rbr))
 				continue;
 		}
-#endif
 
 		buf[i++] = rbr;
 	}
···
 	priv->port.flags = UPF_BOOT_AUTOCONF;
 	priv->port.fifosize = fifosize;
 	priv->port.line = board->line_no;
+	priv->port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_PCH_UART_CONSOLE);
 	priv->trigger = PCH_UART_HAL_TRIGGER_M;
 
 	snprintf(priv->irq_name, IRQ_NAME_SIZE,