leds: pca9633: Add hardware blink support

Add hardware blinking support to the pca9633 driver.

NOTE: Hardware blinking violates the leds infrastructure
driver interface since the hardware only supports
blinking all LEDs with the same delay_on/delay_off
rates.  That is, only the LEDs that are set to blink
will actually blink but all LEDs that are set to blink
will blink in identical fashion.  The delay_on/delay_off
values of the last LED that is set to blink will be used
for all of the blinking LEDs.  If the hardware doesn't
support the requested blinking pattern, a default of
500ms on and off will be used.

Hardware blinking is disabled by default but can be enabled
by setting the 'blink_type' member in the platform_data
struct to 'PCA9633_HW_BLINK' or by adding the 'nxp,hw-blink'
property to the DTS.

(fengguang.wu@intel.com: Removes unneeded semicolon.)

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>