mwifiex: make const arrays static to shink object code size

Don't populate const arrays on the stack, instead make them static
Makes the object code smaller by nearly 300 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
  69260	  16149	    576	  85985	  14fe1	cfg80211.o

After:
   text	   data	    bss	    dec	    hex	filename
  68385	  16725	    576	  85686	  14eb6	cfg80211.o

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>