b43: make const arrays static, reduces object code size

Don't populate const arrays on the stack, instead make them static.
Makes the object code smaller by over 60 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
  14816	   1296	      0	  16112	   3ef0	b43/phy_ht.o

After:
   text	   data	    bss	    dec	    hex	filename
  14551	   1496	      0	  16047	   3eaf	b43/phy_ht.o

(gcc 6.3.0, x86-64)

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