dns_resolver: correct module name in dns resolver documentation

Fix an incorrect module name and sysfs path in dns resolver
documentation.

Signed-off-by: Bharath SM <bharathsm@microsoft.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240324104338.44083-1-bharathsm@microsoft.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>