gpu: imx: Drop parts depending on IMX_DPU_CORE

Those were just removed

Signed-off-by: Guido Günther <guido.gunther@puri.sm>
2 jobs for imx8-4.18-drop-dpu in 42 minutes and 28 seconds
Status Name Job ID Coverage
  Build
passed build:aarch64:Image #18980
librem5

00:42:28

passed build:aarch64:deb #18981
librem5

00:26:15