sparc64: Fix irq stack bootmem allocation.

sparc64: Fix irq stack bootmem allocation.

Currently, irq stack bootmem is allocated for all possible cpus
before nr_cpus value changes the list of possible cpus. As a result,
there is unnecessary wastage of bootmemory.

Move the irq stack bootmem allocation so that it happens after
possible cpu list is modified based on nr_cpus value.

Signed-off-by: Atish Patra <[email protected]>
Reviewed-by: Bob Picco <[email protected]>
Reviewed-by: Vijay Kumar <[email protected]>
Signed-off-by: David S. Miller <[email protected]>