disp: msm: dp: do not skip disconnect when host is unready

usbpd_attention_cb will do dp_display_disconnect_sync, but will
not deinit dp host. usbpd_disconnect_cb can deinit dp host, so
need to check dp state, if dp is unready, should not skip
usbpd_disconnect, can deinit dp host now.

Change-Id: I5a149923ecb043b3a7db973e092bd0d49a715981
Signed-off-by: Zhao, Yuan <yzhao@codeaurora.org>