staging: lustre: move nidstring handling to LNet layer

Moved the source file nidstring.c from libcfs to lnet
since that is the only place it is used. With the
move of nidstring to lnet some functions in libcfs
need to be exported. In later patches those functions
that are only used by LNet also will be moved to the
LNet layer. Also add in missing MAX_NUMERIC_VALUE
defination.

Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>