x86: edison: move CONFIG_BOOTCOMMAND from header file to defconfig

Use defconfig instead of header file for CONFIG_BOOTCOMMAND.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/include/configs/edison.h b/include/configs/edison.h
index 8e312da..7e2f9c1 100644
--- a/include/configs/edison.h
+++ b/include/configs/edison.h
@@ -10,9 +10,6 @@
 
 /* ACPI */
 
-/* Boot */
-#define CONFIG_BOOTCOMMAND "run bootcmd"
-
 /* DISK Partition support */
 
 /* Miscellaneous configurable options */