media: em28xx: make various arrays static const, makes object smaller

Don't populate the arrays on the stack but instead make them
static const. Makes the object code smaller by 767 bytes.

Before:
   text	   data	    bss	    dec	    hex	filename
  41567	  15088	    192	  56847	   de0f	em28xx/em28xx-dvb.o

After:
   text	   data	    bss	    dec	    hex	filename
  39872	  16016	    192	  56080	   db10	em28xx/em28xx-dvb.o

(gcc version 9.2.1, amd64)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>