x86: edison: Move config SYS_MALLOC_LEN to Kconfig

This patch moves the the config SYS_MALLOC_LEN to Kconfig
as it is already done for zynq arch in commit 01aa5b8f0503
("Kconfig: Move config SYS_MALLOC_LEN to Kconfig for zynq").

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/board/intel/edison/Kconfig b/board/intel/edison/Kconfig
index ef9b14a..05d6544 100644
--- a/board/intel/edison/Kconfig
+++ b/board/intel/edison/Kconfig
@@ -12,6 +12,9 @@
 config SYS_CONFIG_NAME
 	default "edison"
 
+config SYS_MALLOC_LEN
+	default 0x08000000
+
 config SYS_TEXT_BASE
 	default 0x01101000