gpiolib: fix poll(2) support reconfigure on sysfs polarity change

Previously enabled poll(2) support on one edge was never reconfigured when
sysfs polarity change was triggered from kernel, because 'struct device
*dev' shadowed an earlier definition.

Found by sparse, which I should've run much earlier.
Signed-off-by: Jani Nikula <ext-jani.1.nikula@nokia.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/gpio/gpiolib.c

@@ -858,8 +858,6 @@ int gpio_sysfs_set_active_low(unsigned gpio, int value)
 	desc = &gpio_desc[gpio];
 
 	if (test_bit(FLAG_EXPORT, &desc->flags)) {
-		struct device *dev;
-
 		dev = class_find_device(&gpio_class, NULL, desc, match_export);
 		if (dev == NULL) {
 			status = -ENODEV;