pps: claim parallel port exclusively

Both pps_parport and pps_gen_parport are written in a way that they
can't share a port with any other driver.  This can result in locking up
the process that loads modules or even the whole kernel if the modules
are compiled in.  Use PARPORT_FLAG_EXCL to indicate this.

Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Cc: Alexander Gordeev <lasaine@lvk.cs.msu.su>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>