fs: debugfs: fix open proxy for unsafe files

In the previous commit referenced below, I had to split
the short fops handling into different proxy fops. This
necessitated knowing out-of-band whether or not the ops
are short or full, when attempting to convert from fops
to allocated fsdata.

Unfortunately, I only converted full_proxy_open() which
is used for the new full_proxy_open_regular() and
full_proxy_open_short(), but forgot about the call in
open_proxy_open(), used for debugfs_create_file_unsafe().

Fix that, it never has short fops.

Fixes: f8f2589 ("fs: debugfs: differentiate short fops with proxy ops")
Reported-by: Suresh Kumar Kurmi <suresh.kumar.kurmi@intel.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202501101055.bb8bf3e7-lkp@intel.com
Reported-by: Venkat Rao Bagalkote <venkat88@linux.vnet.ibm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20250110085826.cd74f3b7a36b.I430c79c82ec3f954c2ff9665753bf6ac9e63eef8@changeid
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/debugfs/file.c

@@ -280,7 +280,7 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
 	const struct file_operations *real_fops = NULL;
 	int r;
 
-	r = debugfs_file_get(dentry);
+	r = __debugfs_file_get(dentry, DBGFS_GET_REGULAR);
 	if (r)
 		return r == -EIO ? -ENOENT : r;