Enable triggered sampling support

configname: CONFIG_IIO_TRIGGER

Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>Industrial I/O support
└─>Enable triggered sampling support
In linux kernel since version 2.6.32 (release Date: 2009-12-02)  
Provides IIO core support for triggers. Currently these
are used to initialize capture of samples to push into
ring buffers. The triggers are effectively a 'capture
data now' interrupt.