x86: edison: Enable DFU timeout

The stock U-Boot on Intel Edison has timeout parameter for DFU command.
Enable it here to be compatible with the original U-Boot configuration.
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>

configs/edison_defconfig

@@ -33,6 +33,7 @@ CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_ENV_OFFSET_REDUND=0x600000
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_CPU=y
+CONFIG_DFU_TIMEOUT=y
 CONFIG_DFU_MMC=y
 CONFIG_DFU_RAM=y
 CONFIG_SUPPORT_EMMC_BOOT=y