arm: zynq: Fix SPL SD boot mode

This patch is fixing two issues:
1. Insufficient stack size for fat fs buffers
2. Insufficient space in malloc area

Tested on zc702 and zc706.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/configs/zynq_zc770_xm011_defconfig b/configs/zynq_zc770_xm011_defconfig
index 357b92b..2b8a12e 100644
--- a/configs/zynq_zc770_xm011_defconfig
+++ b/configs/zynq_zc770_xm011_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_ARCH_ZYNQ=y
 CONFIG_SYS_TEXT_BASE=0x4000000
+CONFIG_SPL_STACK_R_ADDR=0x200000
 # CONFIG_SPL_FAT_SUPPORT is not set
 CONFIG_DEFAULT_DEVICE_TREE="zynq-zc770-xm011"
 CONFIG_FIT=y
@@ -9,6 +10,7 @@
 CONFIG_SYS_EXTRA_OPTIONS="ZC770_XM011"
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_SPL=y
+CONFIG_SPL_STACK_R=y
 CONFIG_SPL_OS_BOOT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="Zynq> "