pxa_lcd: make lcd_enable() a weak pointer

Make lcd_init() a weak pointer so that boards can overload it if necessary.  The
palmtreo680 board needs to wiggle some gpios and configure the pwm controller in
order to get the lcd and its backlight working.

Signed-off-by: Mike Dunn <mikedunn@newsguy.com>

drivers/video/pxa_lcd.c

@@ -410,7 +410,7 @@ void lcd_initcolregs (void)
 #endif /* LCD_MONOCHROME */
 
 /*----------------------------------------------------------------------*/
-void lcd_enable (void)
+__weak void lcd_enable(void)
 {
 }