x86/platform/uv: Fix an error code in uv_hubs_init()

Return -ENOMEM on allocation failure instead of returning random stack
memory contents.

Fixes: 4fc2cf1f

 ("x86/platform/uv: Add new uv_sysfs platform driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Justin Ernst <justin.ernst@hpe.com>
Link: https://lkml.kernel.org/r/X8eoN/jMAJb3H3iv@mwanda