t5r2: explain what "T5R2" is

Thanks to seobrien@ for doing the research here. The Kernel patch that
adds T5R2 support [0] is also related, but didn't seem to have enough
relevant information to warrant including in a comment.

[0]: https://lore.kernel.org/lkml/1309324042-22943-8-git-send-email-djkurtz@chromium.org/t/

BUG=none
TEST=none

Change-Id: I8390d053f0c61f26fbde6f730193f92f174a1108
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/gestures/+/4013428
Commit-Queue: Harry Cutts <hcutts@chromium.org>
Reviewed-by: Torsha Banerjee <torsha@google.com>
Reviewed-by: Sean O'Brien <seobrien@chromium.org>
Reviewed-by: Denis Brockus <dbrockus@chromium.org>
Auto-Submit: Harry Cutts <hcutts@chromium.org>
Tested-by: Harry Cutts <hcutts@chromium.org>
2 files changed