powerpc/fsl_booke: Enable reloading of TLBCAM without switching to AS1

Avoid switching to AS1 when reloading TLBCAM after init for
STRICT_KERNEL_RWX.

When we setup AS1 we expect the entire accessible memory to be mapped
through one entry, this is not the case anymore at the end of init.

We are not changing the size of TLBCAMs, only flags, so no need to
switch to AS1.

So change loadcam_multi() to not switch to AS1 when the given
temporary tlb entry in 0.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a9d517fbfbc940f56103c46b323f6eb8f4485571.1634292136.git.christophe.leroy@csgroup.eu