iwlwifi: fix WGDS check when WRDS is disabled

In the reference BIOS implementation, WRDS can be disabled without
disabling WGDS.  And this happens in most cases where WRDS is
disabled, causing the WGDS without WRDS check and issue an error.

To avoid this issue, we change the check so that we only considered it
an error if the WRDS entry doesn't exist.  If the entry (or the
selected profile is disabled for any other reason), we just silently
ignore WGDS.

Cc: stable@vger.kernel.org # 4.14+
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=205513


Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20200417133700.72ad25c3998b.I875d935cefd595ed7f640ddcfc7bc802627d2b7f@changeid