rfkill: Fixes and cleanup of kernel-doc in the header file

Fixes kerneldoc parameter names to match implementation,
rfkill_set_hw_state(), rfkill_set_sw_state().
Fix description of rfkill_resume_polling().
Fix typos in documentation of rfkill_find_type().
Consistently start kerneldoc description with uppercase
letter.

Signed-off-by: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>