bln: allow separate configuration of blink on and off delays

also minor optimisation of bln_blink_mode check

Change-Id: I9930a42907ab3ef90a85dd065193f5b696b7c061
dt2w: decrease press timeout by 1/2

Change-Id: I1920d8d7951c1353b1252e6ce90e3bca3bbac186