Fix cursor problems

Fix cursor problems

 - Remove size check for a cursor object.
   This size check always failed if it's first request for "set_cursor" with
   the cursor surface because ec->frame is never resized since it was created.
 - Update position values for cursor client.
 - Show/Hide cursor when pointer device is attached/detached by using handlers
   for ECORE_DRM_EVENT_INPUT_ADD/DEL.

Change-Id: I64538317d09105e7a2c3b3257a86705a5e94873c
Signed-off-by: MinJeong Kim <minjjj.kim@samsung.com>