Revert "ath: add support for special 0x0 regulatory domain"

This reverts commit 2dc01659.

Users are reporting regressions in regulatory domain detection and
channel availability.

The problem this was trying to resolve was fixed in firmware anyway:

    QCA6174 hw3.0: sdio-4.4.1: add firmware.bin_WLAN.RMH.4.4.1-00042
    https://github.com/kvalo/ath10k-firmware/commit/4d382787f0efa77dba40394e0bc604f8eff82552

Link: https://bbs.archlinux.org/viewtopic.php?id=254535
Link: http://lists.infradead.org/pipermail/ath10k/2020-April/014871.html
Link: http://lists.infradead.org/pipermail/ath10k/2020-May/015152.html
Link: https://lore.kernel.org/all/1c160dfb-6ccc-b4d6-76f6-4364e0adb6dd@reox.at/
Fixes: 2dc01659 ("ath: add support for special 0x0 regulatory domain")
Cc: <stable@vger.kernel.org>
Cc: Wen Gong <wgong@codeaurora.org>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20200527165718.129307-1-briannorris@chromium.org

drivers/net/wireless/ath/regd.c

@@ -667,14 +667,14 @@ ath_regd_init_wiphy(struct ath_regulatory *reg,
 
 /*
  * Some users have reported their EEPROM programmed with
- * 0x8000 or 0x0 set, this is not a supported regulatory
- * domain but since we have more than one user with it we
- * need a solution for them. We default to 0x64, which is
- * the default Atheros world regulatory domain.
+ * 0x8000 set, this is not a supported regulatory domain
+ * but since we have more than one user with it we need
+ * a solution for them. We default to 0x64, which is the
+ * default Atheros world regulatory domain.
  */
 static void ath_regd_sanitize(struct ath_regulatory *reg)
 {
-	if (reg->current_rd != COUNTRY_ERD_FLAG && reg->current_rd != 0)
+	if (reg->current_rd != COUNTRY_ERD_FLAG)
 		return;
 	printk(KERN_DEBUG "ath: EEPROM regdomain sanitized\n");
 	reg->current_rd = 0x64;