ARM: board-zoom: Do not request LCD panel enable GPIO from twl4030

The pin in question is muxed between GPIO7 and PWM1. For backlight control
there is a custom code in board-zoom-display to control the backlight.
No need to request the GPIO7 - which was failing since the way it is
requested no longer valid: twl's gpio range is allocated dynamically.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>