media: solo6x10: Use managed buffer allocation

Clean up the driver with the new managed buffer allocation API.
The hw_params and hw_free callbacks became superfluous and dropped.

Cc: Bluecherry Maintainers <maintainers@bluecherrydvr.com>
Cc: Anton Sviridenko <anton@corp.bluecherry.net>
Cc: Andrey Utkin <andrey.utkin@corp.bluecherry.net>
Cc: Ismael Luceno <ismael@iodev.co.uk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>