ARM: dts: k2hk-evm: add leds supports

Keystone EVMK2HX supports 4 debug LEDs controlled by GPIO lines as
following (active level is high);

DBG_D1 green gpio12
DBG_D1 red   gpio13
DBG_D1 blue  gpio14
DBG_D1 blue  gpio15

For more information see schematics:
 http://wfcache.advantech.com/www/support/TI-EVM/download/Schematics/PDF/K2H_K2EVM-HK_SCH_A102_Rev1_0.pdf



Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>