ARM: tegra: Remove unused interrupt-parent properties

Some boards are using the interrupt-parent property to point at the GPIO
controller since it handles the interrupts for the GPIO keys. However, a
node needs an interrupts property for interrupt-parent to be meaningful,
which these boards don't have.

gpio-keys in these cases will directly use the GPIO lines specified in
the key definitions and rely on the implicit conversion of those GPIOs
to interrupts by the operating system, so explicit specification of the
interrupts is not required.

Remove the unnecessary interrupt-parent properties.

Signed-off-by: Thierry Reding <treding@nvidia.com>