cpumask: make cpumask_of_cpu_map generic

If an arch doesn't define cpumask_of_cpu_map, create a generic
statically-initialized one for them.  This allows removal of the buggy
cpumask_of_cpu() macro (&cpumask_of_cpu() gives address of
out-of-scope var).

An arch with NR_CPUS of 4096 probably wants to allocate this itself
based on the actual number of CPUs, since otherwise they're using 2MB
of rodata (1024 cpus means 128k).  That's what
CONFIG_HAVE_CPUMASK_OF_CPU_MAP is for (only x86/64 does so at the
moment).

In future as we support more CPUs, we'll need to resort to a
get_cpu_map()/put_cpu_map() allocation scheme.

Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jack Steiner <steiner@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>