show() must not use snprintf() when formatting the value to be
returned to user space.
Fix the following coccicheck warning:
drivers/gpu/drm/panel/panel-dsi-cm.c:251: WARNING: use scnprintf or sprintf.
drivers/gpu/drm/panel/panel-dsi-cm.c:271: WARNING: use scnprintf or sprintf.
Use sysfs_emit instead of scnprintf or sprintf makes more sense.