docs: filesystems: sysfs: Make text and code for ->show() consistent

The documentation says that ->show() should only use sysfs_emit() or
sysfs_emit_at(), but example keeps outdated code. Update the code to
be consistent.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220928135741.54919-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: andy-shev

Documentation/filesystems/sysfs.rst

@@ -263,7 +263,7 @@ A very simple (and naive) implementation of a device attribute is::
     static ssize_t show_name(struct device *dev, struct device_attribute *attr,
 			    char *buf)
     {
-	    return scnprintf(buf, PAGE_SIZE, "%s\n", dev->name);
+	    return sysfs_emit(buf, "%s\n", dev->name);
     }
 
     static ssize_t store_name(struct device *dev, struct device_attribute *attr,