media: dvb-frontends/stv{0910,6111}: constify tables

Mark lookup tables and fe_ops things const so the compiler can put them
into .rodata.

While at it, improve name and identifier strings (moddesc, fe_ops).

Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>