[PATCH] lib: sbi: Apply budget restriction when polling Zkr CSR state transition

[Evgeny Voevodin]

Yes, DEAD is the architectural way to signal a non-functioning source,
and the spec implicitly assumes reasonable timing. The actual scenario
this patch fixes is more specific:

This patch fixes a hang on platforms where either internal entropy
source is event driven and requires corresponding interrupt line to be
enabled or external entropy FIFO refill source is not wired up (as on
SW and HW emulation of Tenstorrent platform).

Without the cap, init_coldboot() spins forever - no console output, no
diagnostic, just a silent boot-time hang. With it, __stack_chk_guard
keeps its compile-time default and the firmware boots.

Given this explanation, is it OK to keep this patch as is or is it
better to send v2 with updated commit message and Kconfig help text?

Thanks,
Evgeny