sparc/leon: Remove on-stack cpumask var

sparc/leon: Remove on-stack cpumask var

In general it's preferable to avoid placing cpumasks on the stack, as
for large values of NR_CPUS these can consume significant amounts of
stack space and make stack overflows more likely.

Use cpumask_subset() and cpumask_first_and() to avoid the need for a
temporary cpumask on the stack.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Dawei Li <dawei.li@shingroup.cn>
Reviewed-by: Andreas Larsson <andreas@gaisler.com>
Tested-by: Andreas Larsson <andreas@gaisler.com>
Link: https://lore.kernel.org/r/20240424025548.3765250-6-dawei.li@shingroup.cn
Signed-off-by: Andreas Larsson <andreas@gaisler.com>