counter: sysfs: remove double return in counter_sysfs_attr_add()

counter: sysfs: remove double return in counter_sysfs_attr_add()

sysfs attribute creation for counter extensions has been consolidated
into a single function, counter_sysfs_exts_add().

Inside counter_sysfs_attr_add(), although the code was changed to return
the result of counter_sysfs_exts_add(), an unreachable return 0;
statement was left at the end of the function.

Remove it.

Fixes: bb4bbbec664f ("counter: Consolidate Counter extension sysfs attribute creation")
Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Link: https://lore.kernel.org/r/20260204180032.514328-1-cosmin-gabriel.tanislav.xa@renesas.com
Signed-off-by: William Breathitt Gray <wbg@kernel.org>