gpu: nova-core: bitfield: Move bitfield-specific code from register! into new macro

gpu: nova-core: bitfield: Move bitfield-specific code from register! into new macro

Move the bitfield-specific code from the register macro into a new macro
called bitfield. This will be used to define structs with bitfields,
similar to C language.

Reviewed-by: Elle Rhumsaa <elle@weathered-steel.dev>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Edwin Peer <epeer@nvidia.com>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Message-ID: <20251016151323.1201196-3-joelagnelf@nvidia.com>