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/ls2080aqds_sdcard_defconfig b/configs/ls2080aqds_sdcard_defconfig
index 590eba6..0f40fa6 100644
--- a/configs/ls2080aqds_sdcard_defconfig
+++ b/configs/ls2080aqds_sdcard_defconfig
@@ -40,6 +40,7 @@
 CONFIG_SPL_BSS_MAX_SIZE=0x100000
 # CONFIG_SPL_SHARES_INIT_SP_ADDR is not set
 CONFIG_SPL_STACK=0x18009ff0
+CONFIG_SYS_SPL_MALLOC=y
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR=y
 CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR=0x8b0
 CONFIG_SPL_ENV_SUPPORT=y