pxa: move mmc drivers to drivers/mmc

introduce new macro CONFIG_PXA_MMC to activate it

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/drivers/mmc/Makefile b/drivers/mmc/Makefile
index 6aa24f5..1b0af12 100644
--- a/drivers/mmc/Makefile
+++ b/drivers/mmc/Makefile
@@ -30,6 +30,7 @@
 COBJS-$(CONFIG_BFIN_SDH) += bfin_sdh.o
 COBJS-$(CONFIG_OMAP3_MMC) += omap3_mmc.o
 COBJS-$(CONFIG_FSL_ESDHC) += fsl_esdhc.o
+COBJS-$(CONFIG_PXA_MMC) += pxa_mmc.o
 
 COBJS	:= $(COBJS-y)
 SRCS	:= $(COBJS:.o=.c)