Revert "patman: use -D option for git format-patch"

Revert "patman: use -D option for git format-patch"

This reverts commit 19b4a3369876f9215e2b861f211e8df1a75e26ca.

Since that commit, patman generates useless patches for file removal;
"git format -D" prints only the header but not the diff when deleting
files, and "git am" always refuses such patches.

The following is the quotation from "man git-format-patch":

  -D, --irreversible-delete
    Omit the preimage for deletes, i.e. print only the header but
    not the diff between the preimage and /dev/null. The resulting
    patch is not meant to be applied with patch nor git apply; this
    is solely for people who want to just concentrate on reviewing
    the text after the change. In addition, the output obviously
    lack enough information to apply such a patch in reverse, even
    manually, hence the name of the option.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Simon Glass <sjg@chromium.org>