boards nrf5340bsim: Remove hwmv1 compatible board definitions

To use this functionality one must now use the hwmv2 naming
(nrf5340bsim/nrf5340/cpu{app,net}).
The old hwmv1 compatible names for these targets,
were left provisionally while all tests in tree were ported.
That being now done, these old names can be removed.

After this change one cannot build anymore
targeting nrf5340bsim_nrf5340_cpu{app,net}
but must instead build targeting
nrf5340bsim/nrf5340/cpu{app,net}
For twister tests the old name were already not valid.

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