serial: 8250: export RSA functions

The RSA functions moved by the below commit to 8250_rsa.c are used in
8250_base.c. Since that can be a module (when CONFIG_SERIAL_8250=m),
this causes build failures:
  ERROR: modpost: "rsa_autoconfig" [drivers/tty/serial/8250/8250_base.ko] undefined!
  ERROR: modpost: "rsa_reset" [drivers/tty/serial/8250/8250_base.ko] undefined!
  ERROR: modpost: "rsa_disable" [drivers/tty/serial/8250/8250_base.ko] undefined!
  ERROR: modpost: "rsa_enable" [drivers/tty/serial/8250/8250_base.ko] undefined!

Fix them by exporting the functions. But only to the base module using
EXPORT_SYMBOL_GPL_FOR_MODULES(). (And not to the whole world.)

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Reported-by: Stephen Rothwell <[email protected]>
Link: https://lore.kernel.org/all/[email protected]/
Fixes: 5a128fb ("serial: 8250: move RSA functions to 8250_rsa.c")
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Jiri Slaby (SUSE)

drivers/tty/serial/8250/8250_rsa.c

@@ -147,6 +147,7 @@ void rsa_enable(struct uart_8250_port *up)
 	if (up->port.uartclk == SERIAL_RSA_BAUD_BASE * 16)
 		serial_out(up, UART_RSA_FRR, 0);
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(rsa_enable, "8250_base");
 
 /*
  * Attempts to turn off the RSA FIFO and resets the RSA board back to 115kbps compat mode. It is
@@ -178,6 +179,7 @@ void rsa_disable(struct uart_8250_port *up)
 		up->port.uartclk = SERIAL_RSA_BAUD_BASE_LO * 16;
 	uart_port_unlock_irq(&up->port);
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(rsa_disable, "8250_base");
 
 void rsa_autoconfig(struct uart_8250_port *up)
 {
@@ -190,6 +192,7 @@ void rsa_autoconfig(struct uart_8250_port *up)
 	if (__rsa_enable(up))
 		up->port.type = PORT_RSA;
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(rsa_autoconfig, "8250_base");
 
 void rsa_reset(struct uart_8250_port *up)
 {
@@ -198,6 +201,7 @@ void rsa_reset(struct uart_8250_port *up)
 
 	serial_out(up, UART_RSA_FRR, 0);
 }
+EXPORT_SYMBOL_GPL_FOR_MODULES(rsa_reset, "8250_base");
 
 #ifdef CONFIG_SERIAL_8250_DEPRECATED_OPTIONS
 #ifndef MODULE