display: Remove display_info interface

display: Remove display_info interface

display_info interface is only used in the wearable plugins.
Thus there is no reason why display_info should exist in all display plugins.
Furthermore, it is hard to figure out above interface usage and role.
Delete display_info to eliminate the dependence between core and display plugins.

During refactoring, the wearable plugin codes must be cleaned up later.

Change-Id: I3caa44fb213cd70416435b02214f0bc0c26edddd
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>