write_name{_quoted_relative,}(): remove redundant parameters

write_name{_quoted_relative,}(): remove redundant parameters

After substitute path_relative() in quote.c with relative_path()
from path.c, parameters (such as len and prefix_len) are redundant
in function write_name() and write_name_quoted_relative().  The
callers have already been audited that the strings they pass are
properly NUL terminated and the length they give are the length of
the string (or -1 that asks the length to be counted by the callee).

Remove these now-redundant parameters.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>