fix(Binding.qml): Remove qml M126 warning

Message:
== and != may perform type coercion, use === or !== to avoid it.

Description:
The non-strict equality comparison is allowed to convert its arguments
to a common type. That can lead to unexpected results such as
' \t\r\n' == 0 being true. Use the strict equality operators === and
!== and be explicit about conversions you require.

Bug-AGL: SPEC-2814

Change-Id: If91ecbc6a1b92c63f7fcdbc94478c58b3aa3e692
Signed-off-by: Li Xiaoming <lixm.fnst@cn.fujitsu.com>