ufs: change isrmdir type to bool or u_int as appropriate

Use bool for isrmdir argument to
ufs_dirremove()/softdep_setup_remove()/newdirrem(), where it is used as
bool.

Use u_int for isrmdir argument to
ufs_dirrewrite()/softdep_setup_directory_change()
where it is 0/1/ino. Without the change to unsigned, the
if (isrmdir > 1)
test is broken on volumes with many inodes.
Use newparent instead of isrmdir for the argument name in this case.

Reviewed by: markj, olce
Tested by: pho
Fixes: 610319c766e941de96e52f2d28fea9f8cfc51aeb
Fixes: 98eb6f0eaa50d8bd9a6794f0a9da2eddeae5bcd8
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D51617