mm: memory_hotplug: cleanup after removal of pfn_valid_within()

When test_pages_in_a_zone() used pfn_valid_within() is has some logic
surrounding pfn_valid_within() checks.

Since pfn_valid_within() is gone, this logic can be removed.

Link: https://lkml.kernel.org/r/20210713080035.7464-3-rppt@kernel.org


Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>