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/nyan-big_defconfig b/configs/nyan-big_defconfig
index 1ffddbe..489ff63 100644
--- a/configs/nyan-big_defconfig
+++ b/configs/nyan-big_defconfig
@@ -27,6 +27,10 @@
 CONFIG_SPL_MAX_FOOTPRINT=0xef8100
 # CONFIG_SPL_SHARES_INIT_SP_ADDR is not set
 CONFIG_SPL_STACK=0x800ffffc
+CONFIG_SYS_SPL_MALLOC=y
+CONFIG_HAS_CUSTOM_SPL_MALLOC_START=y
+CONFIG_CUSTOM_SYS_SPL_MALLOC_ADDR=0x80090000
+CONFIG_SYS_SPL_MALLOC_SIZE=0x10000
 CONFIG_SYS_PROMPT="Tegra124 (Nyan-big) # "
 CONFIG_SYS_MAXARGS=64
 CONFIG_SYS_PBSIZE=2087