rtw89: reduce export symbol number of mac size and quota

An export symbol costs about 40 bytes (in x86 with gcc), so use a structure
containing these small arrays to reduce code size.

   text	   data	    bss	    dec	    hex	filename
  34932	   1410	      0	  36342	   8df6	mac.o (before)
  34276	   1258	      0	  35534	   8ace	mac.o (after)

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220315015522.11366-1-pkshih@realtek.com