ANDROID: drm: Add support for DP 1.4 Compliance edid corruption test

Unlike DP 1.2 edid corruption test, DP 1.4 requires to calculate
real CRC value of the last edid data block, and write it back.
Current edid CRC calculates routine adds the last CRC byte,
and check if non-zero.

This behavior is not accurate; actually, we need to return
the actual CRC value when corruption is detected.
This commit changes this issue by returning the calculated CRC,
and initiate the required sequence.

Change since v7
- Fix for CI.CHECKPATCH

Change since v6
- Add return check

Change since v5
- Obtain real CRC value before dumping bad edid

Change since v4
- Fix for CI.CHECKPATCH

Change since v3
- Fix a minor typo.

Change since v2
- Rewrite checksum computation routine to avoid duplicated code.
- Rename to avoid confusion.

Change since v1
- Have separate routine for returning real CRC.

Change-Id: I6a67007357e5176994f54c4f30c07f42a2d57bd7
Signed-off-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
[abhinavk: resolved conflict with android-5.4's drm_dp_helper.h]
Bug: 139653858
Link: https://patchwork.kernel.org/patch/11375865/


Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>