drm/komeda: Convert sysfs sprintf/snprintf family to sysfs_emit

Fix the following coccicheck warning:
drivers/gpu/drm/arm/display/komeda/komeda_dev.c:97:8-16: WARNING:
use scnprintf or sprintf
drivers/gpu/drm/arm/display/komeda/komeda_dev.c:88:8-16: WARNING:
use scnprintf or sprintf
drivers/gpu/drm/arm/display/komeda/komeda_dev.c:65:8-16: WARNING:
use scnprintf or sprintf

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: James Qian Wang <james.qian.wang@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1617067518-31091-1-git-send-email-tiantao6@hisilicon.com