powerpc/85xx: Enable eSDHC boot support on P2020 DS

We implement our own mmc_get_env_addr since the environment variables are
written to just after the u-boot image on SDCard, so we must read the MBR
to get the start address and code length of the u-boot image, then
calculate the address of the env.

Signed-off-by: Jerry Huang <Chang-Ming.Huang@freescale.com>
Signed-off-by: Zhao Chenhui <b35336@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/board/freescale/common/Makefile b/board/freescale/common/Makefile
index 1abd3e5..8ea5acb 100644
--- a/board/freescale/common/Makefile
+++ b/board/freescale/common/Makefile
@@ -36,6 +36,7 @@
 COBJS-$(CONFIG_PQ_MDS_PIB)	+= pq-mds-pib.o
 COBJS-$(CONFIG_ID_EEPROM)	+= sys_eeprom.o
 COBJS-$(CONFIG_FSL_SGMII_RISER)	+= sgmii_riser.o
+COBJS-$(CONFIG_ENV_IS_IN_MMC)	+= sdhc_boot.o
 
 COBJS-$(CONFIG_MPC8541CDS)	+= cds_pci_ft.o
 COBJS-$(CONFIG_MPC8548CDS)	+= cds_pci_ft.o