mac80211: ath10k: allow failure getting board id via otp

ath10k tries to fetch board id via otp, but that fails for many chips
like QCA988x, QCA9984 etc. Recent commit cc189c0b7f removed the earlier
hack that had allowed QCA radios to work, as that hack was incompatible
with the new wifi chips being introduced to the source tree.

Restore functionality for the existing wifi chips by modifying the
return value of the 'board id via otp' function to a value that is recognised
as a harmless error, so that name evaluation continues by using the board file.

Patch originally suggested by Christian Lamparter in forum discussion.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

package/kernel/mac80211/patches/936-ath10k-fix-otp-failure-result.patch

@@ -0,0 +1,11 @@
+--- a/drivers/net/wireless/ath/ath10k/core.c
++++ b/drivers/net/wireless/ath/ath10k/core.c
+@@ -686,7 +686,7 @@
+ 	if (ret) {
+ 		ath10k_err(ar, "could not execute otp for board id check: %d\n",
+ 			   ret);
+-		return ret;
++		return -EOPNOTSUPP;
+ 	}
+ 
+ 	board_id = MS(result, ATH10K_BMI_BOARD_ID_FROM_OTP);