KVM: PPC: Book3S HV: Nested move LPCR sanitising to sanitise_hv_regs

This will get a bit more complicated in future patches. Move it
into the helper function.

This change allows the L1 hypervisor to determine some of the LPCR
bits that the L0 is using to run it, which could be a privilege
violation (LPCR is HV-privileged), although the same problem exists
now for HFSCR for example. Discussion of the HV privilege issue is
ongoing and can be resolved with a later change.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210412014845.1517916-3-npiggin@gmail.com