ARM: dts: am437x: pixcir_tangoc: use correct flags for irq types

Now IRQs for Pixcir Tangoc touchscreen are defined using
IRQ_TYPE_NONE in am437x-gp-evm.dts and am43x-epos-evm.dts wich
do not correspond HW.

Hence, update am437x-gp-evm.dts and am43x-epos-evm.dts files
and use correct flag IRQ_TYPE_EDGE_FALLING for irq types.

While here, remove duplicated irq declaration for pixcir_ts@5c node
in am437x-gp-evm.dts.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>