media: staging: hantro: avoid future namespace collisions

Rename:
	vp8_dec_mc_filter -> hantro_vp8_dec_mc_filter

As other drivers may end implementing something with the same
name.

So, prepend driver's name here, in order to make symbol namespace
cleaner.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>