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: 387e220a ("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

arch/powerpc/include/asm/book3s/64/mmu.h

@@ -202,7 +202,6 @@ static inline struct subpage_prot_table *mm_ctx_subpage_prot(mm_context_t *ctx)
 /*
  * The current system page and segment sizes
  */
-extern int mmu_linear_psize;
 extern int mmu_virtual_psize;
 extern int mmu_vmalloc_psize;
 extern int mmu_io_psize;
@@ -213,6 +212,7 @@ extern int mmu_io_psize;
 #define mmu_virtual_psize MMU_PAGE_4K
 #endif
 #endif
+extern int mmu_linear_psize;
 extern int mmu_vmemmap_psize;
 
 /* MMU initialization */

arch/powerpc/include/asm/kexec_ranges.h

@@ -9,7 +9,7 @@ struct crash_mem *realloc_mem_ranges(struct crash_mem **mem_ranges);
 int add_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size);
 int add_tce_mem_ranges(struct crash_mem **mem_ranges);
 int add_initrd_mem_range(struct crash_mem **mem_ranges);
-#ifdef CONFIG_PPC_BOOK3S_64
+#ifdef CONFIG_PPC_64S_HASH_MMU
 int add_htab_mem_range(struct crash_mem **mem_ranges);
 #else
 static inline int add_htab_mem_range(struct crash_mem **mem_ranges)