riscv: dts: thead: th1520: Add GPU clkgen reset to AON node

riscv: dts: thead: th1520: Add GPU clkgen reset to AON node

Add the "gpu-clkgen" reset property to the AON device tree node. This
allows the AON power domain driver to detect the capability to power
sequence the GPU and spawn the necessary pwrseq-thead-gpu auxiliary
driver for managing the GPU's complex power sequence.

This commit also adds the prerequisite
dt-bindings/reset/thead,th1520-reset.h include to make the
TH1520_RESET_ID_GPU_CLKGEN available. This include was previously
dropped during a conflict resolution [1].

Link: https://lore.kernel.org/all/aAvfn2mq0Ksi8DF2@x1/
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Drew Fustini <drew@pdp7.com>
Signed-off-by: Michal Wilczynski <m.wilczynski@samsung.com>
Signed-off-by: Drew Fustini <drew@pdp7.com>