ARM: dts: DRA7xx: Add device tree entry for SGX GPU

ARM: dts: DRA7xx: Add device tree entry for SGX GPU

Add SGX GPU device entry to base DRA7x dtsi file.

Let's also leave out SYSC_IDLE_SMART_WKUP as it never has been used in
the known working TI tree. The documentation says SYSC_IDLE_SMART_WKUP
is available, but it's best to stick to a known working solution.

Signed-off-by: Andrew Davis <afd@ti.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Message-ID: <20240109171950.31010-9-afd@ti.com>
[tony@atomide.com: updated description for sysc change]
Signed-off-by: Tony Lindgren <tony@atomide.com>