w1: ds2781: Constify 'struct bin_attribute'

The sysfs core now allows instances of 'struct bin_attribute' to be
moved into read-only memory. Make use of that to protect them against
accidental or malicious modifications.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20241211-sysfs-const-bin_attr-w1-v1-10-c4befd2aa7cc@weissschuh.net


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>