media: mb86a20s: make arrays static const

Don't populate the read-only arrays on the stack but instead them
static const. Also makes the object code smaller by 154 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
  42949	  22424	      0	  65373	   ff5d	media/dvb-frontends/mb86a20s.o

After:
   text	   data	    bss	    dec	    hex	filename
  42731	  22488	      0	  65219	   fec3	media/dvb-frontends/mb86a20s.o

(gcc version 11.2.0)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>