Panel_IT8951: Deassert CS on BUSY timeout in _write_args

[Copilot]

During a multi-word burst in _write_args, a BUSY timeout was returning false without deasserting CS, leaving the panel selected until some outer cleanup path (e.g. endTransaction) ran—which isn't guaranteed on all error paths and can corrupt shared-bus communication.

Change

• Panel_IT8951::_write_args: Call cs_control(true) before returning false on _wait_busy_pin() timeout, ensuring CS is deasserted on every exit path.

if (!_wait_busy_pin())
{
  cs_control(true);  // deassert CS before bailing out
  return false;
}