Simulated uwb-driver for testing uwb-api

[ncasaril]

in hw/drivers/uwb we want a mock/sim driver that implements the uwb api and allows the testing of packages making use of it.

suggested package name: hw/drivers/uwb/uwb_sim

Suitable package to use for first test using this new simulated device is either lib/uwb_pan or lib/twr_ss.