parisc: Avoid ioremap() for same addresss in iosapic_register()

The LBA has already called ioremap() to get it's virtual address,
which can be used for the IOSAPIC as well.
Avoid calling ioremap() again and just reuse the correct
iomem address for the IOSAPIC.

Signed-off-by: Helge Deller <deller@gmx.de>