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/ge_b1x5v2_defconfig b/configs/ge_b1x5v2_defconfig
index 8379b9e..8f33018 100644
--- a/configs/ge_b1x5v2_defconfig
+++ b/configs/ge_b1x5v2_defconfig
@@ -12,6 +12,7 @@
 # CONFIG_GE_RTC is not set
 CONFIG_MX6QDL=y
 CONFIG_TARGET_GE_B1X5V2=y
+CONFIG_SYS_MALLOC_LEN=0xa00000
 CONFIG_DEFAULT_DEVICE_TREE="imx6dl-b1x5v2"
 CONFIG_SPL_TEXT_BASE=0x00908000
 CONFIG_SPL_SERIAL_SUPPORT=y