[Keymap] Update Helix:five_rows OLED code (#14427)

* Stop using snprintf() in keymaps/five_rows/oled_display.c.

The binary size becomes 1350 bytes smaller.

make HELIX=verbose,core-oled helix/rev2/sc:five_rows
(104 bytes over) -> (95%, 1256 bytes free)

make helix/rev3_5rows:five_rows
(528 bytes over) -> (97%, 830 bytes free)

* add matrix scan rate display to OLED for keymaps/five_rows

* add matrix_output_unselect_delay.c to helix keymaps/five_rows

* add GPLv2 header

* apply review comment

1 files changed, 5 insertions, 1 deletions

diff --git a/keyboards/helix/rev3_5rows/keymaps/five_rows/config.h b/keyboards/helix/rev3_5rows/keymaps/five_rows/config.h
index b9961f5c4..e1c124f41 100644
--- a/keyboards/helix/rev3_5rows/keymaps/five_rows/config.h
+++ b/keyboards/helix/rev3_5rows/keymaps/five_rows/config.h
@@ -29,7 +29,11 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
    see tmk_core/common/action_tapping.c */
 
 #undef OLED_UPDATE_INTERVAL
-#define OLED_UPDATE_INTERVAL 50
+#ifdef DEBUG_MATRIX_SCAN_RATE
+#    define OLED_UPDATE_INTERVAL 500
+#else
+#    define OLED_UPDATE_INTERVAL 50
+#endif
 
 // place overrides here