moduleparam: fix kerneldoc

Document missing @arg in xxx_param_cb().
Describe all parameters of module_param_[named_]unsafe() and all
*_param_cb() to make ./scripts/kernel-doc happy.

Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>