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/liteboard_defconfig b/configs/liteboard_defconfig
index 334b22a..24e71bb 100644
--- a/configs/liteboard_defconfig
+++ b/configs/liteboard_defconfig
@@ -24,6 +24,7 @@
 CONFIG_BOOTCOMMAND="mmc dev ${mmcdev};if mmc rescan; then if run loadbootscript; then run bootscript; else if run loadimage; then run mmcboot; else run netboot; fi; fi; else run netboot; fi"
 CONFIG_DEFAULT_FDT_FILE="imx6ul-liteboard.dtb"
 CONFIG_BOARD_EARLY_INIT_F=y
+CONFIG_SYS_SPL_MALLOC=y
 CONFIG_SPL_WATCHDOG=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_MAXARGS=32