parisc: Drop MADV_SPACEAVAIL, MADV_VPS_PURGE and MADV_VPS_INHERIT

Those aren't used or implemented anywhere in Linux.

Furthermore, MADV_SPACEAVAIL seems to be a HP-UX related flag which is
implemented as null operation in HP-UX. And since we don't support running
HP-UX binaries there is no need to keep it.

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