drm/panfrost: Add errata descriptions from kbase

drm/panfrost: Add errata descriptions from kbase

While newer kbase include only the numbers of errata, older kbase
releases included one-line descriptions for each errata, which is useful
for those working on the driver. Import these descriptions. Most are
from kbase verbatim; a few I edited for clarity.

v2: Wrote a description for the workaround of an issue whose cause is
still unknown (Stephen). Errata which pertain to newer models
unsupported by the mainline driver, for which Arm has not yet released
errata information, have been removed from the issue list as the kernel
need not concern itself with these.

v3: Readded errata not yet handled, adding descriptions based on the
workarounds in the latest kbase release.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190823155149.7272-1-alyssa.rosenzweig@collabora.com