params: Prepare for 'const struct module_attribute *'

The 'struct module_attribute' sysfs callbacks are about to change to
receive a 'const struct module_attribute *' parameter.
Prepare for that by avoid casting away the constness through
container_of() and using const pointers to 'struct param_attribute'.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
Link: https://lore.kernel.org/r/20241216-sysfs-const-attr-module-v1-1-3790b53e0abf@weissschuh.net


Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>