nrf52_bsim: Add replacement for nrfx's nrfx_coredep_delay_us()

Provide a replacement for this board for the nordic HAL nrfx
nrfx_coredep_delay_us()
This function is a busy wait, which in the HAL relies on
the ARM DWT or assembler, but which in this board can just
utilize the same busy_wait mechanism provided for k_busy_wait()

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>