[Kernel] src/timer: fix a compile warning

Next ymodem

[bsp] add the linker script file.

Frequent 'C' on the handshake will confuse some sender(lrzsz for
example).

Make fast path fast and slow path slow.

[bsp] add the lpc43xx bsp support.

2. Fix data transfer size calculate error issue;

add some comments of lwip porting

K64f frdm

K64f frdm