Convert CONFIG_SYS_MALLOC_LEN to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_MALLOC_LEN

Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/configs/xilinx_zynqmp_r5_defconfig b/configs/xilinx_zynqmp_r5_defconfig
index 9e0de10..8f3585d 100644
--- a/configs/xilinx_zynqmp_r5_defconfig
+++ b/configs/xilinx_zynqmp_r5_defconfig
@@ -5,6 +5,7 @@
 CONFIG_SYS_MALLOC_F_LEN=0x1000
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_ENV_SIZE=0x20000
+CONFIG_SYS_MALLOC_LEN=0x1400000
 CONFIG_DEFAULT_DEVICE_TREE="zynqmp-r5"
 CONFIG_DEBUG_UART_BASE=0xff010000
 CONFIG_DEBUG_UART_CLOCK=100000000