tty: serial: 8250: Fix another runtime PM usage counter underflow

The commit f9b1122 ("serial: 8250: Fix PM usage_count for console
handover") fixed one runtime PM usage counter balance problem that
occurs because .dev is not set during univ8250 setup preventing call to
pm_runtime_get_sync(). Later, univ8250_console_exit() will trigger the
runtime PM usage counter underflow as .dev is already set at that time.

Call pm_runtime_get_sync() to balance the RPM usage counter also in
serial8250_register_8250_port() before trying to add the port.

Reported-by: Borislav Petkov (AMD) <bp@alien8.de>
Fixes: bedb404 ("serial: 8250_port: Don't use power management for kernel console")
Cc: stable <stable@kernel.org>
Tested-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20241210170120.2231-1-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_core.c

@@ -812,6 +812,9 @@ int serial8250_register_8250_port(const struct uart_8250_port *up)
 			uart->dl_write = up->dl_write;
 
 		if (uart->port.type != PORT_8250_CIR) {
+			if (uart_console_registered(&uart->port))
+				pm_runtime_get_sync(uart->port.dev);
+
 			if (serial8250_isa_config != NULL)
 				serial8250_isa_config(0, &uart->port,
 						&uart->capabilities);