[MIPS] Make SPARSEMEM selectable on QEMU.

This might be helpfull to debug sparsemem on mips.
Signed-off-by: NAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -556,6 +556,7 @@ config QEMU
 	select SYS_HAS_CPU_MIPS32_R1
 	select SYS_SUPPORTS_32BIT_KERNEL
 	select SYS_SUPPORTS_BIG_ENDIAN
+	select ARCH_SPARSEMEM_ENABLE
 	help
 	  Qemu is a software emulator which among other architectures also
 	  can simulate a MIPS32 4Kc system.  This patch adds support for the
@@ -1688,6 +1689,9 @@ config ARCH_DISCONTIGMEM_ENABLE
 	  or have huge holes in the physical address space for other reasons.
 	  See <file:Documentation/vm/numa> for more.
 
+config ARCH_SPARSEMEM_ENABLE
+	bool
+
 config NUMA
 	bool "NUMA Support"
 	depends on SYS_SUPPORTS_NUMA