CHROMIUM: ath10k: add debugfs support for burst mode configuration

This patch adds debugfs support for configuring burst mode to enable
or disable.

f.e,
echo "val" > /sys/kernel/debug/ieee80211/phyX/ath10k/burst_enable
Where disable: val = 0.
      enable : val = 1.

BUG=b:137147192
TEST=1. build image
     2. verify /sys/kernel/debug/ieee80211/phyX/ath10k/burst_enable
        for values set.

Change-Id: Ib5eb4cb9e9358dd2a533b9e6095ed050a184a813
Signed-off-by: Balaji Pothunoori <bpothuno@codeaurora.org>
Signed-off-by: Vamsi Singamsetty <vamssi@codeaurora.org>
Signed-off-by: Mayank Chopra <mak.chopra@codeaurora.org>
Reviewed-on: https://chromium-review.googlesource.com/1739068


Tested-by: Julan Hsu <julanhsu@google.com>
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Kan Yan <kyan@chromium.org>