parisc: Fix invalidate/flush vmap routines

Cache move-in for virtual accesses is controlled by the TLB.  Thus,
we must generally purge TLB entries before flushing.  The flush routines
must use TLB entries that inhibit cache move-in.

V2: Load physical address prior to flushing TLB.  In flush_cache_page,
flush TLB when flushing and purging.

V3: Don't flush when start equals end.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>