i8259A PIC fixes:
- Include size of zero-length i8259a_Private structure in size of memory
allocation for i8259A private data in case it grows in future.
- Take IDT pointer directly from __KernBootPrivate instead of from
KernelBase->kb_PlatformData->kb_APIC; the latter will be NULL if there's
no APIC (which is probably why we're using the i8259A!).
- IRQs on the slave PIC were not disabled during initialisation because of
a typo (">" was used on the mask value instead of ">>"). Fixed.
- Fixed a signedness error with checking the result of probing for a PIC.
Now the PIC can be detected.
git-svn-id: https://svn.aros.org/svn/aros/trunk/AROS@55051 fb15a70f-31f2-0310-bbcc-cdcc74a49acc