cpumask: Relax cpumask_any_but()

Similarly to other cpumask search functions, accept -1, and consider it as
'any CPU' hint. This helps users to avoid coding special cases.

Signed-off-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: James Morse <james.morse@arm.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Fenghua Yu <fenghuay@nvidia.com>
Tested-by: James Morse <james.morse@arm.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Tested-by: Fenghua Yu <fenghuay@nvidia.com>
Link: https://lore.kernel.org/20250515165855.31452-2-james.morse@arm.com