hisax: depend on CONFIG_PNP, not __ISAPNP__

The PNP driver interfaces depend on CONFIG_PNP, so test that rather than
__ISAPNP__.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Karsten Keil <kkeil@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>