mtd: ichxrom: maybe-uninitialized with gcc-4.9

pci_read_config_word() might fail and not initialize its output,
as pointed out by older versions of gcc when using the -Wmaybe-unintialized
flag:

drivers/mtd/maps/ichxrom.c: In function ‘ichxrom_cleanup’:
drivers/mtd/maps/ichxrom.c:63:2: error: ‘word’ is used uninitialized in this function [-Werror=uninitialized]

This is apparently a correct warning, though it does not show up
with newer compilers. Changing the code to not attempt to write
back uninitialized data into PCI config space is a correct
fix for the problem and avoids the warning.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/maps/ichxrom.c

@@ -57,9 +57,11 @@ static void ichxrom_cleanup(struct ichxrom_window *window)
 {
 	struct ichxrom_map_info *map, *scratch;
 	u16 word;
+	int ret;
 
 	/* Disable writes through the rom window */
-	pci_read_config_word(window->pdev, BIOS_CNTL, &word);
+	ret = pci_read_config_word(window->pdev, BIOS_CNTL, &word);
+	if (!ret)
 		pci_write_config_word(window->pdev, BIOS_CNTL, word & ~1);
 	pci_dev_put(window->pdev);