boards: nrf7002dk: Fix SR coexistence GPIOs ownership

In nRF53 SoC, the CPUAPP owns all the GPIOs by default.
Therefore, even if the GPIOs are exclusively used by CPUNET,
we must redefine them for CPUAPP and then set up GPIO
forwarding to CPUNET using SoC registers (this is done as
part of the MPSL CX initialization).

Previously, these GPIOs were mistakenly removed from CPUAPP
and defined only for CPUNET. This caused the GPIOs to be
available for CPUNET but still owned by CPUAPP, breaking
SR coexistence.

Signed-off-by: Murali Thokala <Murali.Thokala@nordicsemi.no>