staging: wfx: make a const array static, makes object smaller

staging: wfx: make a const array static, makes object smaller

Don't populate const array filter_ies on the stack but instead
make it static. Makes the object code smaller by 261 bytes.

Before:
   text	   data	    bss	    dec	    hex	filename
  21674	   3166	    448	  25288	   62c8	drivers/staging/wfx/sta.o

After:
   text	   data	    bss	    dec	    hex	filename
  21349	   3230	    448	  25027	   61c3	drivers/staging/wfx/sta.o

(gcc version 10.2.0)

Reviewed-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20201016223303.687278-1-colin.king@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>