rpi3: Enable SDHost driver in BL2

This patch inits SDHost in BL2 earlysetup. BL2 can start operating mmc
commands to read/write MMC raw blocks.

Signed-off-by: Ying-Chun Liu (PaulLiu) <paulliu@debian.org>
diff --git a/plat/rpi3/platform.mk b/plat/rpi3/platform.mk
index ded92bd..ca638d5 100644
--- a/plat/rpi3/platform.mk
+++ b/plat/rpi3/platform.mk
@@ -31,6 +31,9 @@
 				drivers/delay_timer/delay_timer.c	\
 				drivers/delay_timer/generic_delay_timer.c \
 				drivers/rpi3/gpio/rpi3_gpio.c		\
+				drivers/io/io_block.c			\
+				drivers/mmc/mmc.c			\
+				drivers/rpi3/sdhost/rpi3_sdhost.c	\
 				plat/common/aarch64/platform_mp_stack.S	\
 				plat/rpi3/aarch64/plat_helpers.S	\
 				plat/rpi3/aarch64/rpi3_bl2_mem_params_desc.c \