tty/serial: Migrate cpm_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 <dima@arista.com>
Link: https://lore.kernel.org/r/20191213000657.931618-15-dima@arista.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/cpm_uart/cpm_uart_core.c

@@ -40,10 +40,6 @@
 #include <asm/fs_pd.h>
 #include <asm/udbg.h>
 
-#if defined(CONFIG_SERIAL_CPM_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
-#define SUPPORT_SYSRQ
-#endif
-
 #include <linux/serial_core.h>
 #include <linux/kernel.h>
 
@@ -347,9 +343,7 @@ static void cpm_uart_int_rx(struct uart_port *port)
 		/* ASSUMPTION: it contains nothing valid */
 		i = 0;
 	}
-#ifdef SUPPORT_SYSRQ
 	port->sysrq = 0;
-#endif
 	goto error_return;
 }
 
@@ -1204,7 +1198,8 @@ static int cpm_uart_init_port(struct device_node *np,
 	pinfo->port.uartclk = ppc_proc_freq;
 	pinfo->port.mapbase = (unsigned long)mem;
 	pinfo->port.type = PORT_CPM;
-	pinfo->port.ops = &cpm_uart_pops,
+	pinfo->port.ops = &cpm_uart_pops;
+	pinfo->port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_CPM_CONSOLE);
 	pinfo->port.iotype = UPIO_MEM;
 	pinfo->port.fifosize = pinfo->tx_nrfifos * pinfo->tx_fifosize;
 	spin_lock_init(&pinfo->port.lock);