libertas: reduce debug output

This patch tries to make dmesg logs between different runs easier
to compare by

* removing the jiffies (use CONFIG_PRINTK_TIME if you need
  timing)
* remove the line numbers, they change with each applied patch

It also changes the deprecated __FUNCTION__ to __func__ to make
checkpatch.pl happy.

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>