Convert CONFIG_SYS_SPL_MALLOC_SIZE et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_SPL_MALLOC_SIZE
   CONFIG_SYS_SPL_MALLOC_START

We introduce a default value here as well, and CONFIG_SYS_SPL_MALLOC to
control if we have a malloc pool or not.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/ventana_defconfig b/configs/ventana_defconfig
index f3389b0..87e4d10 100644
--- a/configs/ventana_defconfig
+++ b/configs/ventana_defconfig
@@ -16,6 +16,10 @@
 CONFIG_SPL_MAX_FOOTPRINT=0x8000
 # CONFIG_SPL_SHARES_INIT_SP_ADDR is not set
 CONFIG_SPL_STACK=0xffffc
+CONFIG_SYS_SPL_MALLOC=y
+CONFIG_HAS_CUSTOM_SPL_MALLOC_START=y
+CONFIG_CUSTOM_SYS_SPL_MALLOC_ADDR=0x90000
+CONFIG_SYS_SPL_MALLOC_SIZE=0x10000
 CONFIG_SYS_PROMPT="Tegra20 (Ventana) # "
 CONFIG_SYS_MAXARGS=64
 CONFIG_SYS_PBSIZE=2085