fft_eval: add support for ath10k sample format

This patch is losely based on Sven Eckelmanns original patch, but
contains a lot refactoring to support both the ath9k and ath10k format
without duplicating too much code. Also the DC interpolation / max_exp
calculation have been moved into the driver, as it is for ath9k.

Tests have been performed using a 5.8 GHz analogue tv repeater. Note
that the ath10k format may still change.

Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
fft_eval: add 5.8 ghz tv repeater samples

Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>