CHROMIUM: ath10k: Refine relay fs code for CFR dump

Refine relay fs for CFR and make it generic and later new relay fs
node can be easily added.

BUG=b:132147953
TEST=None

Change-Id: I6229776a56fe50763ec643740906561cdc63333e
Signed-off-by: Yi Chen <yichen@codeaurora.org>
Signed-off-by: Vamsi Singamsetty <vamssi@codeaurora.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1695226


Reviewed-by: Julan Hsu <julanhsu@google.com>
Tested-by: Julan Hsu <julanhsu@google.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>