locks: Fix procfs output for file leases

Since commit 778fc546 ("locks: fix tracking of inprogress
lease breaks"), leases break don't change @fl_type but modifies
@fl_flags. However, procfs's part haven't been updated.

Previously, for a breaking lease the target type was printed (see
target_leasetype()), as returns fcntl(F_GETLEASE). But now it's always
"READ", as F_UNLCK no longer means "breaking". Unlike the previous
one, this behaviour don't provide a complete description of the lease.

There are /proc/pid/fdinfo/ outputs for a lease (the same for READ and
WRITE) breaked by O_WRONLY.
-- before:
lock:   1: LEASE  BREAKING  READ  2558 08:03:815793 0 EOF
-- after:
lock:   1: LEASE  BREAKING  UNLCK  2558 08:03:815793 0 EOF

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>