[media] saa7134: remove unused log_err() macro

As reported by Masanari, this macro is using "KERN_ERR"
instead of "KERN_ERROR". That would lead into a compilation
breakage, if this macro were used somewhere inside the driver.

Instead of fixing the macro, as originally proposed, let's just
remove the dead code.

Reported-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>