modules: hal_nordic: Update nrfx to version 1.8.1

Update nrfx to the recently released version. See
https://github.com/NordicSemiconductor/nrfx/blob/v1.8.1/CHANGELOG.md
for a list of changes that this version introduces.

Origin: nrfx
License: BSD 3-Clause
URL: https://github.com/NordicSemiconductor/nrfx/tree/v1.8.1


commit: ecc3616b8ea766ba0c921681258463696ad47930
Purpose: Provide peripheral drivers for Nordic SoCs
Maintained-by: External

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>