leds: Add SN3218 and SN3216 support to the IS31FL32XX driver
Si-En Technology was acquired by ISSI in 2011, and it appears that
the IS31FL3218/IS31FL3216 are just rebranded SN3218/SN3216 devices.
Add the "si-en,sn3218" and "si-en,sn3216" compatible strings into the
IS31FL32XX driver as aliases for the issi equivalents, and update
binding documentation.
Signed-off-by: David Rivshin <drivshin@allworx.com> Acked-by: Rob Herring <robh@kernel.org> Tested-by: Stefan Wahren <stefan.wahren@i2se.com> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>