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/flea3_defconfig b/configs/flea3_defconfig
index 631dd3e..dad74a1 100644
--- a/configs/flea3_defconfig
+++ b/configs/flea3_defconfig
@@ -9,6 +9,7 @@
 CONFIG_SYS_I2C_MXC_I2C2=y
 CONFIG_SYS_I2C_MXC_I2C3=y
 CONFIG_SYS_LOAD_ADDR=0x80800000
+CONFIG_SYS_MALLOC_LEN=0x110000
 CONFIG_FIT=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_BOOTDELAY=3