media: media/platform/sti: fix kernel-doc formatting

bdisp/bdisp-filter.h: coef: -> @coef:  (missing @)
c8sectpfe/c8sectpfe-debugfs.h: /** -> /* (wasn't a kernel-doc comment)
sti/hva/hva.h: @v4l2: -> @vbuf:  (wrong name)

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: Jean-Christophe Trotin <jean-christophe.trotin@st.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>