drupal_get_schema: unconsistent $name parameter

In drupal_get_schema(), the parameter $name should IMHO be renamed to $table.

$name is confusing, as it could just as well represent the module name that is for example expected as parameter by drupal_install_schema($module).
But here it represents the table name, as in drupal_write_record($table), where this parameter has already been named $table.

The patch is straightforward and should not cause any side effects.