Upgrade nrf52833-hal and nrf51-hal to 0.16

[BartMassey]

The nrf52833-hal and nrf51-hal crates are currently at 0.14 here. This leads to getting an old version of nrf-usbd, which in turn leads to getting an old version of critical-section. This makes linking broken unless the client of this crate also uses the cortex-m crate with feature critical-section-single-core. I'm not sure what other kinds of issues and vulnerabilities are here, so it seems to be best to just upgrade the hal crates: this seems to compile fine.

Let me know if I'm confused somehow.