2.adjust some viable and micro name
3.some other small fix

This reverts commit 5aeedc4f, reversing
changes made to 3d80e414.

This merge breaks every uart driver in all BSPs. @bright-pan , is there
any way to get this done without breaking existing code?

Add hardware flow support.
Use new struct serial_ringbuffer.

Pass USB CV test verification;
Code cleanup;

This issue causes fstat & lseek not correct.

fix msh_exec(char* cmd, rt_size_t length) bug

I have to mention that this bug is introduced by myself, in the last
commit <fd07f30f> to dfs_nfs.c