ARM: dts: am437x-gp-evm: Add wakeup interrupt source for pixcir_i2c_ts

On am437x-gp-evm, pixcir_i2c_ts can wakeup the system from low power
state via pinctrl and IO daisy chain using generic wakeirq framework.
With commit 3fffd128 ("i2c: allow specifying separate wakeup
interrupt in device tree") i2c core allows optional wakeirq to be
specified via device tree. Add wakeup irq entry to enable pixcir_i2c_ts
to wake the system from low power state.

Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>