hwmon: (w83793) make const array watchdog_minors static, reduces object code size

Don't populate const array watchdog_minors on the stack, instead make it
static. Makes the object code smaller by over 350 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
  48019	  38144	    256	  86419	  15193	drivers/hwmon/w83793.o

After:
   text	   data	    bss	    dec	    hex	filename
  47574	  38232	    256	  86062	  1502e	drivers/hwmon/w83793.o

(gcc 6.3.0, x86-64)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>