[MIPS] Sparsemem fixes

1. MIPS should select SPARSEMEM_STATIC since allocating bootmem in
   memory_present() will corrupt bootmap area.
2. pfn_valid() for SPARSEMEM is defined in linux/mmzone.h

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 3ebc5b2..330f6ab 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1694,6 +1694,7 @@
 
 config ARCH_SPARSEMEM_ENABLE
 	bool
+	select SPARSEMEM_STATIC
 
 config NUMA
 	bool "NUMA Support"