When CONFIG_RELOCATABLE=n, the Linux real mode interrupt handlers call
into KVM using real address. This needs to be translated to the kernel
linear effective address before the MMU is switched on.

kvmppc_bad_host_intr misses adding these bits, so when it is used to
handle a system reset interrupt (that always gets delivered in real
mode), it results in an instruction access fault immediately after
the MMU is turned on.

Fix this by ensuring the top 2 address bits are set when the MMU is
turned on.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>