wireless: Convert wiphy_debug macro to function

Save a few bytes of text

(allyesconfig)
$ size drivers/net/wireless/built-in.o*
   text	   data	    bss	    dec	    hex	filename
3924568	 100548	 871056	4896172	 4ab5ac	drivers/net/wireless/built-in.o.new
3926520	 100548	 871464	4898532	 4abee4	drivers/net/wireless/built-in.o.old

$ size net/wireless/core.o*
   text	   data	    bss	    dec	    hex	filename
  12843	    216	   3768	  16827	   41bb	net/wireless/core.o.new
  12328	    216	   3656	  16200	   3f48	net/wireless/core.o

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>