fb: JZ4770: Removed leftovers of old panel interface
fb: JZ4770: Add support for a display area smaller than the full panel

This is useful for displays that have overscan, like TVs.
ASoC: JZ4770: GCW0: Add error reporting for headphone plug detection

Even seemingly simple things can fail and this went unnoticed because
the return values were ignored.
mips: JZ4770: GPIO: Add to_irq handler

While the documentation says this is optional, that doesn't seem to be
the case anymore: IRQ lookup for the headphone plug detection fails if
there is no to_irq handler.