Add AVR32 LCD support

This patch adds support for the AVR32 LCD controller.  This patch is
based off the latest u-boot-video.

A quick summary of what's going on:-

Enable LCDC pixel clock
Enable LCDC port pins
Add framebuffer pointer to global_data struct
Allocate framebuffer

To use the new code, update your board config to include something like
this:-

#define CONFIG_LCD			1

#if defined(CONFIG_LCD)
#define CONFIG_CMD_BMP
#define CONFIG_ATMEL_LCD		1
#define LCD_BPP				LCD_COLOR16
#define CONFIG_BMP_16BPP		1
#define CONFIG_FB_ADDR			0x10600000
#define CONFIG_WHITE_ON_BLACK		1
#define CONFIG_VIDEO_BMP_GZIP 		1
#define CONFIG_SYS_VIDEO_LOGO_MAX_SIZE		262144
#define CONFIG_ATMEL_LCD_BGR555		1
#define CONFIG_SYS_CONSOLE_IS_IN_ENV	1
#define CONFIG_SPLASH_SCREEN		1
#endif

The standard U-Boot BMP and Splash-screen features should just work.

Signed-off-by: Mark Jackson <mpfj@mimc.co.uk>
[agust@denx.de: fixed some style issues]
Signed-off-by: Anatolij Gustschin <agust@denx.de>