iio: kfifo - add poll support.
iio: kfifo - add poll support.

This buffer implementation was missing poll support.

Signed-off-by: Jonathan Cameron <09f65b71b7655725897b2fd41a09a0cefe2e1ace@kernel.org>
Tested-by: Lars-Peter Clausen <3318dc5ce3e4fb7c28a0b841b6801c884e1d0896@metafoo.de>
Acked-by: srinivas pandruvada <910e550f1c830a1d246b6c3ed4d6ca559ba95c19@intel.com>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs