PPC: booke206: Check for min/max TLB entry size

When setting a TLB entry, we need to check if the TLB we're putting it in
actually supports the given size. According to the 2.06 PowerPC ISA, a
value that's out of range can either be redefined to something implementation
dependent or we can raise an illegal opcode exception. We do the latter.

Signed-off-by: Alexander Graf <agraf@suse.de>
