Add a basic GPU node for mt8183.

Signed-off-by: Nicolas Boichat <redacted>
---
The binding we use with out-of-tree Mali drivers includes more
clocks, this is used for devfreq: the out-of-tree driver switches
clk_mux to clk_sub_parent (26Mhz), adjusts clk_main_parent, then
switches clk_mux back to clk_main_parent:
(see https://chromium.googlesource.com/chromiumos/third_party/kernel/+/chromeos-4.19/drivers/gpu/arm/midgard/platform/mediatek/mali_kbase_runtime_pm.c#423)
clocks =
        <&topckgen CLK_TOP_MFGPLL_CK>,
        <&topckgen CLK_TOP_MUX_MFG>,
        <&clk26m>,
        <&mfgcfg CLK_MFG_BG3D>;
clock-names =
        "clk_main_parent",
        "clk_mux",
        "clk_sub_parent",
        "subsys_mfg_cg";
(based on discussions, this probably belongs in the clock core)

This only matters for devfreq, that is disabled anyway as we don't
have platform-specific code to handle >1 supplies.

(no changes since v6)

Changes in v6:
 - Add gpu regulators to kukui dtsi as well.
 - Power domains are now attached to spm, not scpsys
 - Drop R-B.

Changes in v5:
 - Rename "2d" power domain to "core2" (keep R-B again).

Changes in v4:
 - Add power-domain-names to describe the 3 domains.
   (kept Alyssa's reviewed-by as the change is minor)

Changes in v3:
 - No changes

Changes in v2:
 - Use sram instead of mali_sram as SRAM supply name.
 - Rename mali@ to gpu@.

 arch/arm64/boot/dts/mediatek/mt8183-evb.dts   |   6 +
 .../arm64/boot/dts/mediatek/mt8183-kukui.dtsi |   6 +
 arch/arm64/boot/dts/mediatek/mt8183.dtsi      | 105 ++++++++++++++++++
 3 files changed, 117 insertions(+)

diff --git a/arch/arm64/boot/dts/mediatek/mt8183-evb.dts b/arch/arm64/boot/dts/mediatek/mt8183-evb.dts
index cba2d8933e79..0a8c2fad8e16 100644
--- a/arch/arm64/boot/dts/mediatek/mt8183-evb.dts
+++ b/arch/arm64/boot/dts/mediatek/mt8183-evb.dts

@@ -42,6 +42,12 @@ &auxadc {
 	status = "okay";
 };
 
+&gpu {
+	supply-names = "mali", "sram";