media: fc001[23]: make const gain table arrays static

Don't populate the gain tables on the stack but make them static const.
Makes the object code smaller:

Before:
   text	   data	    bss	    dec	    hex	filename
   7801	   1408	      0	   9209	   23f9	drivers/media/tuners/fc0012.o
   8483	    936	      0	   9419	   24cb	drivers/media/tuners/fc0013.o

After:
   text	   data	    bss	    dec	    hex	filename
   7696	   1464	      0	   9160	   23c8	drivers/media/tuners/fc0012.o
   8362	   1024	      0	   9386	   24aa	drivers/media/tuners/fc0013.o

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