media: drxd: make const array fastIncrDecLUT static

Don't populate array fastIncrDecLUT on the stack but instead make it
static. Makes the object code smaller by over 360 bytes:

   text	   data	    bss	    dec	    hex	filename
  32680	    944	     64	  33688	   8398	drxd_hard.o

   text	   data	    bss	    dec	    hex	filename
  32223	   1040	     64	  33327	   822f	drxd_hard.o

(gcc version 7.2.0 x86_64)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>