qt: make QtDeclarative depend on QtSql

As indicated by QtDeclarative.pc, QtDeclarative needs QtSql.
It builds fine without it, but then you get a run-time error.
So add QtSql to the QtDeclarative depends-on list.

Signed-off-by: Danomi Manchego <danomimanchego123@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>