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/omap4_panda_defconfig b/configs/omap4_panda_defconfig
index 23599cf..c51627d 100644
--- a/configs/omap4_panda_defconfig
+++ b/configs/omap4_panda_defconfig
@@ -14,6 +14,8 @@
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_SPL_MAX_SIZE=0xbc00
+CONFIG_SYS_SPL_MALLOC=y
+CONFIG_SYS_SPL_MALLOC_SIZE=0x800000
 # CONFIG_SPL_FS_EXT4 is not set
 # CONFIG_SPL_I2C is not set
 # CONFIG_SPL_NAND_SUPPORT is not set