common: vivaldi: modify key struct to be overridable

change common struct key to be overridable
let board layer can customize row col struct.

BUG=b:220996030
BRANCH=none
TEST=build make -j BOARD=Banshee pass

Signed-off-by: Leo-Tsai <leocx_tsai@compal.corp-partner.google.com>
Change-Id: Ic86a24b82ddee1c59474971e042ff06d69f6d69a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3535539
Reviewed-by: Elthan Huang <elthan_huang@compal.corp-partner.google.com>
Tested-by: Elthan Huang <elthan_huang@compal.corp-partner.google.com>
Reviewed-by: Boris Mittelberg <bmbm@google.com>

Author: Leo-Tsai

common/keyboard_vivaldi.c

@@ -21,7 +21,7 @@
  * Row Column info for Top row keys T1 - T15. This has been sourced from
  * go/vivaldi-matrix (internal link for vivaldi scan matrix spec).
  */
-static const struct key {
+__overridable const struct key {
 	uint8_t row;
 	uint8_t col;
 } vivaldi_keys[] = {