arm64/mm: Make vmemmap_free() available only with CONFIG_MEMORY_HOTPLUG

vmemmap_free() callsites (mm/sparse.c) and declaration (include/linux/mm.h)
are protected with CONFIG_MEMORY_HOTPLUG. This function is not required if
CONFIG_MEMORY_HOTPLUG is not enabled. Hence move the config wrapper outside
the function definition.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/1621842030-23256-1-git-send-email-anshuman.khandual@arm.comSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/mm/mmu.c

@@ -1166,16 +1166,17 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 	return 0;
 }
 #endif	/* !ARM64_SWAPPER_USES_SECTION_MAPS */
+
+#ifdef CONFIG_MEMORY_HOTPLUG
 void vmemmap_free(unsigned long start, unsigned long end,
 		struct vmem_altmap *altmap)
 {
-#ifdef CONFIG_MEMORY_HOTPLUG
 	WARN_ON((start < VMEMMAP_START) || (end > VMEMMAP_END));
 
 	unmap_hotplug_range(start, end, true, altmap);
 	free_empty_tables(start, end, VMEMMAP_START, VMEMMAP_END);
-#endif
 }
+#endif /* CONFIG_MEMORY_HOTPLUG */
 
 static inline pud_t *fixmap_pud(unsigned long addr)
 {