Fix user-visible spelling error

Pavel Machek reports a warning about W+X pages found in the "Persisent"
kmap area.  After grepping for it (using the correct spelling), and not
finding it, I noticed how the debug printk was just misspelled.  Fix it.

The actual mapping bug that Pavel reported is still open.  It's
apparently a separate issue from the known EFI page tables, looks like
it's related to the HIGHMEM mappings.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/x86/mm/dump_pagetables.c

@@ -89,7 +89,7 @@ static struct addr_marker address_markers[] = {
 	{ 0/* VMALLOC_START */, "vmalloc() Area" },
 	{ 0/*VMALLOC_END*/,     "vmalloc() End" },
 # ifdef CONFIG_HIGHMEM
-	{ 0/*PKMAP_BASE*/,      "Persisent kmap() Area" },
+	{ 0/*PKMAP_BASE*/,      "Persistent kmap() Area" },
 # endif
 	{ 0/*FIXADDR_START*/,   "Fixmap Area" },
 #endif