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.

Datasheets:
    IS31FL3218: http://www.issi.com/WW/pdf/31FL3218.pdf
    SN3218:     http://www.si-en.com/uploadpdf/s2011517171720.pdf

    IS31FL3216: http://www.issi.com/WW/pdf/31FL3216.pdf
    SN3216:     http://www.si-en.com/uploadpdf/SN3216201152410148.pdf

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>
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 08a5743..1f64151 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -572,9 +572,9 @@
 	tristate "LED support for ISSI IS31FL32XX I2C LED controller family"
 	depends on LEDS_CLASS && I2C && OF
 	help
-	  Say Y here to include support for ISSI IS31FL32XX LED controllers.
-	  They are I2C devices with multiple constant-current channels, each
-	  with independent 256-level PWM control.
+	  Say Y here to include support for ISSI IS31FL32XX and Si-En SN32xx
+	  LED controllers. They are I2C devices with multiple constant-current
+	  channels, each with independent 256-level PWM control.
 
 comment "LED driver for blink(1) USB RGB LED is under Special HID drivers (HID_THINGM)"