mac80211: ath9k: handle error from copy_to_user in read_file_eeprom

Handle error from copy_to_user in read_file_eeprom.
Fix compilarion warning:
/__w/openwrt/openwrt/openwrt/build_dir/target-x86_64-openwrt-linux-musl_musl/linux-x86_64/backports-6.1.24/drivers/net/wireless/ath/ath9k/debug.c: In function 'read_file_eeprom':
/__w/openwrt/openwrt/openwrt/build_dir/target-x86_64-openwrt-linux-musl_musl/linux-x86_64/backports-6.1.24/drivers/net/wireless/ath/ath9k/debug.c:1451:17: error: ignoring return value of 'copy_to_user' declared with attribute 'warn_unused_result' [-Werror=unused-result]
 1451 |                 copy_to_user(user_buf, from, bytes);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Signed-off-by: Christian Marangi <[email protected]>

package/kernel/mac80211/patches/ath9k/500-ath9k_eeprom_debugfs.patch

@@ -1,6 +1,6 @@
 --- a/drivers/net/wireless/ath/ath9k/debug.c
 +++ b/drivers/net/wireless/ath/ath9k/debug.c
-@@ -1413,6 +1413,53 @@ void ath9k_deinit_debug(struct ath_softc
+@@ -1413,6 +1413,54 @@ void ath9k_deinit_debug(struct ath_softc
  	ath9k_cmn_spectral_deinit_debug(&sc->spec_priv);
  }
  
@@ -39,7 +39,8 @@
 +		} else {
 +			bytes = 2;
 +		}
-+		copy_to_user(user_buf, from, bytes);
++		if (copy_to_user(user_buf, from, bytes))
++			return -EFAULT;
 +		user_buf += bytes;
 +	}
 +	return *ppos - pos;