gpu: nova-core: add helper function to wait on condition

While programming the hardware, we frequently need to busy-wait until
a condition (like a given bit of a register to switch value) happens.

Add a basic `wait_on` helper function to wait on such conditions
expressed as a closure, with a timeout argument.

This is temporary as we will switch to `read_poll_timeout` [1] once it
is available.

Link: https://lore.kernel.org/lkml/20250220070611.214262-8-fujita.tomonori@gmail.com/

 [1]
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250619-nova-frts-v6-11-ecf41ef99252@nvidia.com


Signed-off-by: Danilo Krummrich <dakr@kernel.org>