powerpc/64s: Fix build failure when CONFIG_PPC_64S_HASH_MMU is not set

powerpc/64s: Fix build failure when CONFIG_PPC_64S_HASH_MMU is not set

The following build failure occurs when CONFIG_PPC_64S_HASH_MMU is not
set:

    arch/powerpc/kernel/setup_64.c: In function ‘setup_per_cpu_areas’:
    arch/powerpc/kernel/setup_64.c:811:21: error: ‘mmu_linear_psize’ undeclared (first use in this function); did you mean ‘mmu_virtual_psize’?
      811 |                 if (mmu_linear_psize == MMU_PAGE_4K)
          |                     ^~~~~~~~~~~~~~~~
          |                     mmu_virtual_psize
    arch/powerpc/kernel/setup_64.c:811:21: note: each undeclared identifier is reported only once for each function it appears in

Move the declaration of mmu_linear_psize outside of
CONFIG_PPC_64S_HASH_MMU ifdef.

After the above is fixed, it fails later with the following error:

    ld: arch/powerpc/kexec/file_load_64.o: in function `.arch_kexec_kernel_image_probe':
    file_load_64.c:(.text+0x1c1c): undefined reference to `.add_htab_mem_range'

Fix that, too, by conditioning add_htab_mem_range() symbol to
CONFIG_PPC_64S_HASH_MMU.

Fixes: 387e220a2e5e ("powerpc/64s: Move hash MMU support code under CONFIG_PPC_64S_HASH_MMU")
Reported-by: Erhard F. <erhard_f@mailbox.org>
Signed-off-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=215567
Link: https://lore.kernel.org/r/20220301204743.45133-1-muriloo@linux.ibm.com