ARM: dts: am437x-gp-evm: Enable wkup_m3 control of IO isolation

With this flag wkup_m3 is able to control IO isolation during
suspend on the board.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Drew Fustini <dfustini@baylibre.com>
Message-Id: <20220502021508.1342869-2-dfustini@baylibre.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>