drivers: tee: improve sysfs interface by using sysfs_emit()

drivers: tee: improve sysfs interface by using sysfs_emit()

Replace scnprintf() with sysfs_emit() while formatting buffer that is
passed to userspace as per the recommendation in
Documentation/filesystems/sysfs.rst. sysfs _show() callbacks should use
sysfs_emit() or sysfs_emit_at() while returning values to the userspace.
This change does not impact functionality, but aligns with sysfs
interface usage guidelines for the tee driver.

Signed-off-by: Akhilesh Patil <akhilesh@ee.iitb.ac.in>
Reviewed-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>