[ARM] pxa/idp: remove the unnecessary idp_init_irq()

TOUCH_PANEL_IRQ is never referenced, and set_irq_type() shouldn't
be called in this way, remove it, as well as the idp_init_irq(),
and use pxa25x_init_irq() instead.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Cc: Cliff Brake <cliff.brake@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>