x86: cacheinfo: correct return value when cache_disable feature is not active

x86: cacheinfo: correct return value when cache_disable feature is not active

Impact: bug fix

If user writes to "cache_disable" attribute on a CPU that does not support
this feature, the process hangs due to an invalid return value in
store_cache_disable().

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Langsdorf <mark.langsdorf@amd.com>
LKML-Reference: <20090409130729.GH31527@alberich.amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>