powerpc/8xx: Allow setting DATA alignment even with STRICT_KERNEL_RWX

It is now possible to not pin kernel text with a 8Mbytes TLB, so
the alignment for STRICT_KERNEL_RWX can be relaxed.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/d0d8b05012b392dd166cfd911f14ba2741ce7e1e.1724173828.git.christophe.leroy@csgroup.eu