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/omap5_uevm_defconfig b/configs/omap5_uevm_defconfig
index 53ae1e6..03b8745 100644
--- a/configs/omap5_uevm_defconfig
+++ b/configs/omap5_uevm_defconfig
@@ -17,6 +17,8 @@
 CONFIG_DEFAULT_FDT_FILE="omap5-uevm.dtb"
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_SPL_MAX_SIZE=0x1dc00
+CONFIG_SYS_SPL_MALLOC=y
+CONFIG_SYS_SPL_MALLOC_SIZE=0x800000
 # CONFIG_SPL_NAND_SUPPORT is not set
 CONFIG_SPL_OS_BOOT=y
 CONFIG_SPL_FALCON_BOOT_MMCSD=y