ARM: mm: fix boot on SA1110 Assabet

Commit 83db0384 (mm/ARM: use common help functions to free reserved
pages) broke booting on the Assabet by trying to convert a PFN to
a virtual address using the __va() macro.  This macro takes the
physical address, not a PFN.  Fix this.

Cc: <stable@vger.kernel.org> # 3.10
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/init.c

@@ -600,7 +600,7 @@ void __init mem_init(void)
 
 #ifdef CONFIG_SA1111
 	/* now that our DMA memory is actually so designated, we can free it */
-	free_reserved_area(__va(PHYS_PFN_OFFSET), swapper_pg_dir, 0, NULL);
+	free_reserved_area(__va(PHYS_OFFSET), swapper_pg_dir, 0, NULL);
 #endif
 
 	free_highpages();