lcd: split splash code into its own function

lcd: split splash code into its own function

lcd_logo() currently performs tasks well beyond just displaying the logo.
It has code which displays splash image, it has logic which determines
when the different display features are displayed, and it is coupled with
the lcd console because it holds the responsibility of returning the
lcd console base address.

Make lcd_logo() just about the logo by:
* Moving splash image display code into a dedicated function
* Moving the logic regarding when various features are displayed to
  lcd_clear() (which is arguably not the correct name for housing such
  code either, but it is currently the most fitting location code wise)
* Move the responsibility of setting the console base address to
  lcd_clear() too.

Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Bo Shen <voice.shen@atmel.com>
Tested-by: Josh Wu <josh.wu@atmel.com>
Cc: Bo Shen <voice.shen@atmel.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Anatolij Gustschin <agust@denx.de>