powerpc/book3s: Add an HV variant of FIXUP_ENDIAN that is recoverable

Add an HV variant of FIXUP_ENDIAN which uses HSRR[01] and does not
clear MSR[RI], which improves recoverability.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>