sfc: modify allocation error message

Change error message when alloc_cpumask_var fails.

Repairs "cpumask: convert drivers/net/sfc".

Signed-off-by: Mike Travis <travis@sgi.com>
Acked-by: Ben Hutchings <bhutchings@solarflare.com>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>