CHROMIUM: ath10k: Add a check to know ath10k_hif_diag_read support

ath10k_hif_diag_read is supported only in discrete wifi chipset
ex: Cascade/Besra and not supported in integrated wifi radio
ex:Adrestea+Cherokee. This leads to improper behaviour when mem_value
debugfs entry is read for integrated wifi radio as it calls
ath10k_hif_diag_read op.

To fix this improper behaviour, add a check before calling ath10k_hif_diag_read
to know whether such operation is supported or not.

BUG=b:140398965
TEST=1. Compilation
     2. cat/sys/kernel/debug/ieee80211/phyX/ath10k/mem_value

Change-Id: If8d4bdf2ec8817246bb5c8f48045d4b6099714e8
Signed-off-by: Surabhi Vishnoi <svishnoi@codeaurora.org>
Reviewed-on: https://chromium-review.googlesource.com/1789366
Tested-by: Zhihong Yu <zhihongyu@chromium.org>
Commit-Ready: Zhihong Yu <zhihongyu@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Zhihong Yu <zhihongyu@chromium.org>
1 file changed