display: Remove check_seed_status()

display: Remove check_seed_status()

The check_seed_status() name and role is unclear.
Thus it is removed and devided to 3 funcs.

These functions are added to display core.
- void display_set_initial_brightness(void);
    -> It checks default brightness and set initial brightness value.
- void display_set_initial_battery_flag(void);
    -> It checks battery status and set battery status to pm_status_flag.
- void display_set_initial_lockscreen_status(void);
    -> It checks lockscreen state and set initial lockscreen timeout value.

To relocate these, this function is added to display-plugin.
- int display_plugin_config_get_pm_default_brightness(int *pm_default_brightness);

Change-Id: Ia1be19b5c0d5643e42c5c56a5b8df9483d25ad9b
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>