module.h: allow #define strings to work with MODULE_IMPORT_NS

The MODULE_IMPORT_NS() macro does not allow defined strings to work
properly with it, so add a layer of indirection to allow this to happen.

Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Matthias Maennich <maennich@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>