media: stv0910: read and update mod_cod in read_status()

Add missing state->modcod update from upstream driver which needs to be
done when manage_matype_info() sets is_vcm on certain S2 transponders.

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