rtlwifi: rtl8821ae: Fix 5G detection problem

The changes associated with moving this driver from staging to the regular
tree missed one section setting the allowable rates for the 5GHz band.

This patch is needed to fix the regression reported in Bug #88811
(https://bugzilla.kernel.org/show_bug.cgi?id=88811).

Reported-by: Valerio Passini <valerio.passini@unicam.it>
Tested-by: Valerio Passini <valerio.passini@unicam.it>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Valerio Passini <valerio.passini@unicam.it>
Signed-off-by: John W. Linville <linville@tuxdriver.com>