[media] et61x251: Use current logging styles

Add pr_fmt and convert printks to pr_<level>
Remove explicit prefixes from logging messages.
One of the prefixes was defective, a copy/paste error.
Use ##__VA_ARGS__ for variadic macros.
Whitespace neatening.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>