util: Delete flash_pd.py
util: Delete flash_pd.py

Reasons:
1. We integrated pd into ec for all recent projects. So after Skylake,
we don't need it anymore.
2. For old project, they can find it in firmware branch.

BUG=chromium:1031705
BRANCH=master
TEST=None

Signed-off-by: kerker <b60348db21a0b73e8345c1da67719faa1d4da16e@chromium.org>
Change-Id: I8975a0d61058b9c95c7c681c17cf1c543cffeaac
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2434587
Reviewed-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Commit-Queue: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Tested-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec