powerpc: Fix hypervisor facility unavaliable vector number

Currently if we take hypervisor facility unavaliable (from 0xf80/0x4f80) we
mark it as an OS facility unavaliable (0xf60) as the two share the same code
path.

The becomes a problem in facility_unavailable_exception() as we aren't able to
see the hypervisor facility unavailable exceptions.

Below fixes this by duplication the required macros.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Cc: <stable@vger.kernel.org> [v3.10]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>