video/lcd: double buffer: use db for android

android need double buffer support

when check_var, if the application need more buffer memory, we free the old
buffer, and allocate new buffers according to the request buffer size.
if reallocate successful, we will also update the DMA Addr register

android will use yoffset to swap the DMA address, so we cannot reset it

Signed-off-by: LiuXin <liuxing@embedinfo.com>
video/lcd: double buffer: fix flicker caused by db

android use double buffer, it will swap the DMA address when a new frame
is ready. at this point, the former frame may still be drawing by the lcd
controller.
so don't update dma address register immediately in fb_pan_display, just
update dma descriptor

in fbmem.c, it will call fb_pan_display after fb_set_par, so I think we don't
need to call update_dma in fb_set_par, because in fb_pan_display we also called
update_dma. there is repeated!
but we still need to initialize DMA engine, so put it to proble function

Signed-off-by: LiuXin <liuxing@embedinfo.com>
video/lcd: vsync: add vsync support

android will use vsync to driver application draw pictures and
surfaceflinger to do composite

Signed-off-by: LiuXin <liuxing@embedinfo.com>
video/lcd: avoid FIFO underflow error

1. In order to avoid FIFO underflow, let base layer data is retrieved
through AHB 1 while not AHB 0

2. Increase right_margin, so DMA have enough time to move the data
Also increase pixclock, so the frame rate will not drop

Signed-off-by: LiuXin <liuxing@embedinfo.com>
Signed-off-by: Royce Jiang <jiangxd@embedinfo.com>
video/lcd: let android toast display well

some android toast's size is very small, the line alignment will cause
them display abnormal

Signed-off-by: LiuXin <liuxing@embedinfo.com>
Merge remote-tracking branch 'sdc_android/avrcodev/embest/dev/liuxin/3.10/lcd_display' into linux-3.10-at91_fbdev_vsync
Revert "video/lcd: avoid FIFO underflow error"

This reverts commit e36a21cf8c6551573c1a27f478a1ba33a924ca2c.
Only reverts the at91 board, drivers keep the same.