MIPS: JZ4770: GCW0: Power panel on/off via platform-lcd driver

We used to have a custom panel interface for this, but platform-lcd
offers similar functionality in a looser coupled way.
fb: JZ4770: Removed panel hooks

We had a custom interface to power on/off the LCD panel. However, the
existing platform-lcd driver can handle this just fine, so this commit
removes the custom interface.

Since the panel hooks were the only contents of the platform data,
the platform data for this driver is removed completely.
MIPS: JZ4770: Add cpu-feature-overrides.h

By defining the present and absent CPU features at compile time, the
compiler only has to generate the code paths that will actually be used
for this particular CPU.
MIPS: JZ4770: Moved platform devices header into arch/mips/jz4770/

It is included by platform.c and by the board files.
MIPS: JZ4770: GCW0: Include platform devices header from new location