memory: bt1-l2-ctl: replace scnprintf() with sysfs_emit()

Documentation/filesystems/sysfs.rst mentions that show() should only
use sysfs_emit() or sysfs_emit_at() when formating the value to be
returned to user space. So replace scnprintf() with sysfs_emit().

Signed-off-by: Salah Triki <salah.triki@gmail.com>
Link: https://lore.kernel.org/r/aBkw_p9GkH2fm2UJ@pc


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>