drivers/leds/leds-pca9532.c: add gpio capability

Allow unused leds on pca9532 to be used as gpio.  The board I am working
on now has no less than 6 pca9532 chips.  One chips is used for only leds,
one has 14 leds and 2 gpio and the rest of the chips are gpio only.

There is also one board in mainline which could use this capabilty;
arch/arm/mach-iop32x/n2100.c
 232         {       .type = PCA9532_TYPE_NONE }, /* power OFF gpio */
 233         {       .type = PCA9532_TYPE_NONE }, /* reset gpio */

This patch defines a new pin type, PCA9532_TYPE_GPIO, and registers a
gpiochip if any pin has this type set.  The gpio will registers all chip
pins but will filter on gpio_request.

[randy.dunlap@oracle.com: fix build when GPIOLIB is not enabled]
Signed-off-by: Joachim Eastwood <joachim.eastwood@jotron.com>
Reviewed-by: Wolfram Sang <w.sang@pengutronix.de>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Jan Weitzel <j.weitzel@phytec.de>
Cc: Juergen Kilb <j.kilb@phytec.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>