ymodem: fix examples due to new API
romfs: check the dirent before use it

System will crash when the romfs is erased. Add checks before using them
to avoid it.
romfs: rewrite mkromfs.py
Merge pull request #368 from grissiom/romfs-next

Romfs next
Merge pull request #367 from grissiom/ymodem-fix

ymodem: fix examples due to new API
[BSP] Add GCC compiler support for mb9bf568r
Merge pull request #369 from BernardXiong/master

[BSP] Add GCC compiler support for mb9bf568r