Target for nrf5340-net-pac in the README is incorrect

[Tomer-Eliahu]

From reading the product info for the nRF5340, it seems like only the application core has a FPU.
My understanding is that the target for the nrf5340-network core should then be set to thumbv8m.main-none-eabi instead of what it is now in the readme: thumbv8m.main-none-eabihf.

Apologies if I have missed something.