Revert "gpu: drm: bridge: improve the function of getting training status"

This reverts commit 1d6d6a6a.

After upgrading u-boot to version 2022.04, this patch is no longer
needed.

Signed-off-by: Meng Li <Meng.Li@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>