media: cx24120: Add retval check for cx24120_message_send()

[ Upstream commit 96002c0ac824e1773d3f706b1f92e2a9f2988047 ]

If cx24120_message_send() returns error, we should keep local struct
unchanged.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 5afc9a25 ("[media] Add support for TechniSat Skystar S2")
Signed-off-by: Daniil Dulov <d.dulov@aladdin.ru>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sasha Levin <sashal@kernel.org>