Fix: some cards caused slews of card detect interrupts.
Fix: some cards caused slews of card detect interrupts.

- Certain SD cards would cause a large number of card detect interrupts,
  which would overwhelm the RTOS' deferred operation queue.
- Changed SD driver config to use "GPIO" card detect, which effectively
  disables it since we don't have GPIO card detect implemented.

flit/modular,flit/modular,flit/modular,flit/modular,flit/modular