parisc: SEABIOS_HPPA_VERSION 15

Fixes and enhancements:
- Fix OpenBSD 7.4 boot (PDC_MEM_MAP call returned wrong values)
- Minor enhancements to show if a 64-bit SeaBIOS-hppa firmware
  is used

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