rtlwifi: rtl8821ae: Remove unused GET_XXX and SET_XXX descriptor macros

As the first step in converting from macros that get/set information
in the RX and TX descriptors, unused macros are being removed.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>