[media] SOLO6x10: remove unneeded register locking and barriers

readl() and writel() are atomic, we don't need the spin lock.
Also, flushing posted write buffer isn't required. Especially on read :-)

Signed-off-by: Krzysztof Ha?asa <khalasa@piap.pl>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>