media: ddbridge/max: prefix lnb_init_fmode() and fe_attach_mxl5xx()

Add a ddb_ prefix to the two functions to better avoid conflicts in the
global namespace, ie. when building everything into the kernel image.

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