MGS-2731 gpu: dts: fix the wrong clock config for 7ulp gpu shader

MGS-2731 gpu: dts: fix the wrong clock config for 7ulp gpu shader

gc7000nu has only clk2x core input, no external shader clock input,
currently gpu_3d_shader clock is set to the 2d bus clock mistakenly,

should set gpu_3d_shader config with dummy clock in gpu device,
also removed the unused gpu2d_shader_clock setting from dts.

Signed-off-by: Xianzhong <xianzhong.li@nxp.com>
(cherry picked from commit 021b397e2594a37987d852a382f90bf0559fcf30)