pinctrl: JZ4770: Add "no_pins" group and add it to the "lcd" function
MIPS: JZ4770: GCW0: When the LCD sleeps, select "no_pins" group

This will disable the actual LCD pins, putting them in pulled-up input
mode, which we hope saves power over keeping them configured in the LCD
function.
fb: JZ4770: Switch to sleep pinctrl state when display is blanked

We don't need a signal on the LCD pins when the panel is off.