staging: slicoss: clean up use of dev_err

First, don't print pci device information or driver prefixes, this
is already printed by dev_err. Next, don't report error messages
via dev_err when the failing function already reports all errors
via dev_err.

Signed-off-by: David Matlack <matlackdavid@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>