git-am --whitespace: do not lose the command line option

git-am --whitespace: do not lose the command line option

When you start "git am --whitespace=fix" and the patch application process
is interrupted by an unapplicable patch early in the series, after
fixing the offending patch, the remainder of the patch should be processed
still with --whitespace=fix when restarted with "git am --resolved" (or
dropping the offending patch with "git am --skip").

The breakage was introduced by the commit 67dad68 (add -C[NUM] to git-am,
2007-02-08); this should fix it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>