gfs2/sysfs: Replace sprintf/snprintf with sysfs_emit

gfs2/sysfs: Replace sprintf/snprintf with sysfs_emit

Documentation/filesystems/sysfs.rst mentions that show() should only
use sysfs_emit() or sysfs_emit_at() when formatting values returned
to user space. This patch updates the GFS2 sysfs interface accordingly.

It replaces uses of sprintf() and snprintf() in all *_show() functions
with sysfs_emit() to align with current kernel sysfs API best practices.
It also updates the TUNE_ATTR_2 macro to use sysfs_emit() instead of
snprintf().

Signed-off-by: Utkarsh Singh <utkarsh.singh.em@gmail.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>