Revert incorrect calculation introduced in
commit ec5a787da2 ("Bluetooth: controller: Fix multiple
master role event scheduling") and revert a related
incorrect fix in commit a02606cbf9 ("Bluetooth:
controller: Fix missing ticks to us conversion").
Fixes the controller assert in ctrl.c line number 1477. A
64-bit arithmetic took ~35 us in Radio ISR for nRF51 causing
the ISR to take too much time before packet buffer could be
set.
Also, fixed master scheduling by correctly accounting for
the jitter between each master event.
Relates to: #5486
Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>