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/phycore-am335x-r2-wega_defconfig b/configs/phycore-am335x-r2-wega_defconfig
index 0bd348b..95905b4 100644
--- a/configs/phycore-am335x-r2-wega_defconfig
+++ b/configs/phycore-am335x-r2-wega_defconfig
@@ -24,6 +24,8 @@
 CONFIG_DEFAULT_FDT_FILE="am335x-wega-rdk.dtb"
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_ARCH_MISC_INIT=y
+CONFIG_SYS_SPL_MALLOC=y
+CONFIG_SYS_SPL_MALLOC_SIZE=0x800000
 CONFIG_SPL_I2C=y
 CONFIG_SPL_MTD_SUPPORT=y
 CONFIG_SPL_NAND_DRIVERS=y