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/da850evm_nand_defconfig b/configs/da850evm_nand_defconfig
index 8218d95..f8f38b7 100644
--- a/configs/da850evm_nand_defconfig
+++ b/configs/da850evm_nand_defconfig
@@ -11,6 +11,7 @@
 CONFIG_SYS_MALLOC_F_LEN=0x800
 CONFIG_ENV_SIZE=0x20000
 CONFIG_ENV_OFFSET=0x0
+CONFIG_SYS_MALLOC_LEN=0x110000
 CONFIG_DM_GPIO=y
 CONFIG_DEFAULT_DEVICE_TREE="da850-evm"
 CONFIG_SPL_TEXT_BASE=0x80000000