gpu: nova-core: convert falcon registers to kernel register macro

gpu: nova-core: convert falcon registers to kernel register macro

Convert all PFALCON, PFALCON2 and PRISCV registers to use the kernel's
register macro and update the code accordingly.

Because they rely on the same types to implement relative registers,
they need to be updated in lockstep.

nova-core's local register macro is now unused, so remove it.

Reviewed-by: Gary Guo <gary@garyguo.net>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260325-b4-nova-register-v4-8-bdf172f0f6ca@nvidia.com
[acourbot@nvidia.com: remove unused import.]
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>