media: vpif: don't generate a kernel-doc warning on a constant

Constants documentation is not supported by kernel-doc markups.
So, change the comment label to avoid this warning:
	drivers/media/platform/davinci/vpif.c:54: warning: cannot understand function prototype: 'const struct vpif_channel_config_params vpif_ch_params[] = '

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>