Move dmapool.c to mm/ directory

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index b39ea3f..ed0a722 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -5,7 +5,7 @@
 			   cpu.o firmware.o init.o map.o devres.o \
 			   attribute_container.o transport_class.o
 obj-y			+= power/
-obj-$(CONFIG_HAS_DMA)	+= dma-mapping.o dmapool.o
+obj-$(CONFIG_HAS_DMA)	+= dma-mapping.o
 obj-$(CONFIG_ISA)	+= isa.o
 obj-$(CONFIG_FW_LOADER)	+= firmware_class.o
 obj-$(CONFIG_NUMA)	+= node.o