esp: fix section mismatch warning

Not critical.

  WARNING: drivers/char/esp.o(.text+0x278): Section mismatch in reference from the function show_serial_version() to the variable .init.data:serial_version
  The function show_serial_version() references
  the variable __initdata serial_version.
  This is often because show_serial_version lacks a __initdata
  annotation or the annotation of serial_version is wrong.

  WARNING: drivers/char/esp.o(.text+0x27d): Section mismatch in reference from the function show_serial_version() to the variable .init.data:serial_name
  The function show_serial_version() references
  the variable __initdata serial_name.
  This is often because show_serial_version lacks a __initdata
  annotation or the annotation of serial_name is wrong.
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Andrew J. Robinson <arobinso@nyx.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/esp.c

@@ -2258,7 +2258,7 @@ static int esp_open(struct tty_struct *tty, struct file *filp)
  * driver.
  */
 
-static void show_serial_version(void)
+static void __init show_serial_version(void)
 {
 	printk(KERN_INFO "%s version %s (DMA %u)\n",
 		serial_name, serial_version, dma);