xfs: add support for FS_IOC_GETFSSYSFSPATH

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Link: https://lore.kernel.org/r/20240207025624.1019754-7-kent.overstreet@linux.dev


Signed-off-by: Christian Brauner <brauner@kernel.org>