rpi3: Enable GPIO in BL2

This patch inits the GPIO in BL2 earlysetup. So BL2 can start operating
GPIO pins.

Signed-off-by: Ying-Chun Liu (PaulLiu) <paulliu@debian.org>
diff --git a/plat/rpi3/platform.mk b/plat/rpi3/platform.mk
index 5e76345..ded92bd 100644
--- a/plat/rpi3/platform.mk
+++ b/plat/rpi3/platform.mk
@@ -27,6 +27,10 @@
 				drivers/io/io_fip.c			\
 				drivers/io/io_memmap.c			\
 				drivers/io/io_storage.c			\
+				drivers/gpio/gpio.c			\
+				drivers/delay_timer/delay_timer.c	\
+				drivers/delay_timer/generic_delay_timer.c \
+				drivers/rpi3/gpio/rpi3_gpio.c		\
 				plat/common/aarch64/platform_mp_stack.S	\
 				plat/rpi3/aarch64/plat_helpers.S	\
 				plat/rpi3/aarch64/rpi3_bl2_mem_params_desc.c \