rcaps: Drop keyboard layout information to get a valid country code

Previously fallback data like us.intl would have been dropped as invalid
data as it was longer than the 2 character country code.
Now anything (usually keyboard layout info) after the dot is removed to
get a valid country code.

Bug: 419726281
Change-Id: I57346b42fe940de6f7954dc7493eee2d815f497e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6578394
Auto-Submit: Christoph Schlosser <cschlosser@chromium.org>
Commit-Queue: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Nicolas Dossou-Gbété <dgn@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1464940}