ARM: pxa: magician: Rename abstract LCD GPIOs

This patch renames GPIOs, which are used to control the power lines to
the LCD screen. New names correspond to a real functionality, which was
measured on the HTC Magician board_id 0x3a.

Signed-off-by: Petr Cvek <petr.cvek@tul.cz>
Acked-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>