fs: export may_create() as may_create_dentry()

fs: export may_create() as may_create_dentry()

For many years btrfs as been using a copy of may_create() in
fs/btrfs/ioctl.c:btrfs_may_create(). Everytime may_create() is updated we
need to update the btrfs copy, and this is a maintenance burden. Currently
there are minor differences between both because the btrfs side lacks
updates done in may_create().

Export may_create() so that btrfs can use it and with the less generic
name may_create_dentry().

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Link: https://patch.msgid.link/ce5174bca079f4cdcbb8dd145f0924feb1f227cd.1768307858.git.fdmanana@suse.com
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>