serial: silence section mismatch warnings in 8250_pci

Fix following warnings:
WARNING: drivers/serial/built-in.o(.data+0x5b8): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:pci_ite887x_exit()
WARNING: drivers/serial/built-in.o(.data+0x5e0): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:pci_plx9050_exit()
WARNING: drivers/serial/built-in.o(.data+0x608): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:pci_plx9050_exit()
WARNING: drivers/serial/built-in.o(.data+0x658): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:pci_plx9050_exit()
WARNING: drivers/serial/built-in.o(.data+0x680): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:pci_plx9050_exit()
WARNING: drivers/serial/built-in.o(.data+0x6a8): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:pci_plx9050_exit()
WARNING: drivers/serial/built-in.o(.data+0x6d0): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:sbs_exit()
WARNING: drivers/serial/built-in.o(.data+0x6f8): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:sbs_exit()
WARNING: drivers/serial/built-in.o(.data+0x720): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:sbs_exit()
WARNING: drivers/serial/built-in.o(.data+0x748): Section mismatch in reference from the variable pci_serial_quirks to the function .devexit.text:sbs_exit()

pci_serial_quirks contains a number of function pointers where the referenced
function is annotated __devexit.  This is OK so we annotate pci_serial_quirks
with __refdata to ignore the __devexit references

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/serial/8250_pci.c

@@ -775,7 +775,7 @@ pci_default_setup(struct serial_private *priv, struct pciserial_board *board,
  * This list is ordered alphabetically by vendor then device.
  * Specific entries must come before more generic entries.
  */
-static struct pci_serial_quirk pci_serial_quirks[] = {
+static struct pci_serial_quirk pci_serial_quirks[] __refdata = {
 	/*
 	* ADDI-DATA GmbH communication cards <info@addi-data.com>
 	*/