powerpc/mm/64s: Move THP reqs into a separate symbol

Move the Kconfig symbols related to transparent hugepages (THP) under a
separate config symbol, separate from CONFIG_PPC_BOOK3S_64.

The new symbol is automatically enabled if CONFIG_PPC_BOOK3S_64 is
enabled, so there is no behaviour change, except for the existence of
the new PPC_THP symbol.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240823032911.1238471-1-mpe@ellerman.id.au

Author: mpe

arch/powerpc/platforms/Kconfig.cputype

@@ -84,11 +84,8 @@ config PPC_BOOK3S_64
 	bool "Server processors"
 	select PPC_FPU
 	select PPC_HAVE_PMU_SUPPORT
-	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
-	select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 	select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION
 	select ARCH_ENABLE_SPLIT_PMD_PTLOCK
-	select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
 	select ARCH_SUPPORTS_HUGETLBFS
 	select ARCH_SUPPORTS_NUMA_BALANCING
 	select HAVE_MOVE_PMD
@@ -108,6 +105,13 @@ config PPC_BOOK3E_64
 
 endchoice
 
+config PPC_THP
+       def_bool y
+       depends on PPC_BOOK3S_64
+       select HAVE_ARCH_TRANSPARENT_HUGEPAGE
+       select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+       select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
+
 choice
 	prompt "CPU selection"
 	help