kernfs: don't fail listing extended attributes
Userspace doesn't expect a failure to list extended attributes:
$ ls -lA /sys/
ls: /sys/: No data available
ls: /sys/kernel: No data available
ls: /sys/power: No data available
ls: /sys/class: No data available
ls: /sys/devices: No data available
ls: /sys/dev: No data available
ls: /sys/hypervisor: No data available
ls: /sys/fs: No data available
ls: /sys/bus: No data available
ls: /sys/firmware: No data available
ls: /sys/block: No data available
ls: /sys/module: No data available
total 0
drwxr-xr-x 2 root root 0 Jan 1 1970 block
drwxr-xr-x 52 root root 0 Jan 1 1970 bus
drwxr-xr-x 88 root root 0 Jan 1 1970 class
drwxr-xr-x 4 root root 0 Jan 1 1970 dev
drwxr-xr-x 11 root root 0 Jan 1 1970 devices
drwxr-xr-x 3 root root 0 Jan 1 1970 firmware
drwxr-xr-x 10 root root 0 Jan 1 1970 fs
drwxr-xr-x 2 root root 0 Jul 2 09:43 hypervisor
drwxr-xr-x 14 root root 0 Jan 1 1970 kernel
drwxr-xr-x 251 root root 0 Jan 1 1970 module
drwxr-xr-x 3 root root 0 Jul 2 09:43 power
Fix it by simply reporting success when no extended attributes are
available instead of reporting ENODATA.
Link: https://lore.kernel.org/78b13bcdae82ade95e88f315682966051f461dde.camel@linaro.org
Fixes:
d1f4e9026007 ("kernfs: remove iattr_mutex") # mainline only
Reported-by: André Draszik <andre.draszik@linaro.org>
Link: https://lore.kernel.org/20250819-ahndung-abgaben-524a535f8101@brauner
Signed-off-by: Christian Brauner <brauner@kernel.org>