Make uClinux burned to stm32f429 successfully

Change second and third line of FLASH_CMD in mk/flash.mak
	-f interface/stlink-v2.cfg \
    	-f target/stm32f4x_stlink.cfg \
	, which make error while burning
	to -f /board/stm32f429discovery.cfg \
Merge pull request #4 from joshsyu/master

Update the usage of stm32f429 configurations for openocd