modules: hal_nordic: Add missing nrfx_config entries for nRF54L15

Add nrfx_grtc related entries that were introduced in nrfx 3.4.0,
especially NRFX_GRTC_CONFIG_AUTOSTART that should be by default
set to 1.

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