paride: pf driver fixes

The pf driver for parallel port floppy drives seems to be broken.  At least
with Imation SuperDisk with EPAT chip, the driver calls pi_connect() and
pi_disconnect after each transferred sector.  At least with EPAT, this
operation is very expensive - causes drive recalibration.  Thus, transferring
even a single byte (dd if=/dev/pf0 of=/dev/null bs=1 count=1) takes 20
seconds, making the driver useless.

The pf_next_buf() function seems to be broken as it returns 1 always (except
when pf_run is non-zero), causing the loop in do_pf_read_drq (and
do_pf_write_drq) to be executed only once.

The following patch fixes this problem.  It also fixes swapped descriptions in
pf_lock() function and removes DBMSG macro, which seems useless.

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>