display: Relocate auto-brightness.c from display core to wearable plugin

The function of auto-brightness.c is only used by wearable plugin.
Thus auto-brightness.c file is moved to wearable/display module.

Change-Id: I301801f9325d6a09969070499a14dd0c38b0ba17
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>

diff --git a/src/display/plugin-common/auto-brightness.c b/plugins/wearable/display/auto-brightness.c
similarity index 100%
rename from src/display/plugin-common/auto-brightness.c
rename to plugins/wearable/display/auto-brightness.c