nfs: fix bug

I have to mention that this bug is introduced by myself, in the last
commit <fd07f30f511335f506ae6557e300093d4dde421e> to dfs_nfs.c
add operating definitions of UART0 to UART5
support UART0 to UART5 straightly
add RT_USING_UARTx and set console via uart0
add CM_PER_UARTx_CLKCTRL
[Kernel] application module can support arguments
[DFS] remove a compiling warning
kernel: rearrange the header file include order

There are some CONFIG OPTIONS in rtdebug.h, which may influence the
rtdef.h, so rtdebug.h should be head of the rtdef.h
Merge pull request #228 from prife/kernel

kernel: rearrange the header file include order
friendly for uart count under 6
Update msh.c

fix msh_exec(char* cmd, rt_size_t length) bug
Update msh.c
Update msh.c
Merge pull request #231 from roamboy/master

Update msh.c
[Finsh] fix strncmp issue in command search
[Kernel] Fix the compiling issue for not including rtconfig.h file in rtdebug.h/rtdef.h
update CMSIS version to 3.20
Add sector size check when mounting a FAT file system.
Include rtconfig.h file in rtdebug.h file.
Merge pull request #235 from aozima/pulls

update CMSIS version to 3.20