powerpc/32s: Make local symbols non visible in hash_low.

In hash_low.S, a lot of named local symbols are used instead of
numbers to ease code readability. However, they don't need to be
visible.

In order to ease blacklisting of functions running with MMU
disabled for kprobe, rename the symbols to .Lsymbols in order
to hide them as if they were numbered labels.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/90c430d9e0f7af772a58aaeaf17bcc6321265340.1585670437.git.christophe.leroy@c-s.fr