Scan rate is too slow for HHKB JP?

[tmk]

I found dropping key occasionally when making a line on qwertuiop[] in a row with one finger quickly.
It seems like scan rate is too slow for HHKB JP. In comparison with Pro2 JP has twice size of matrix so it has to scan at twice speed of Pro2 theoretically.

This change seems to cure the problem. But very short test and review are only done yet.

--- a/keyboard/hhkb/matrix.c
+++ b/keyboard/hhkb/matrix.c
@@ -132,7 +132,7 @@ uint8_t matrix_scan(void)

             // NOTE: KEY_STATE keep its state in 20us after KEY_ENABLE.
             // This takes 25us or more to make sure KEY_STATE returns to idle state.
-            _delay_us(75);
+            _delay_us(30);
         }
         if (matrix[row] ^ matrix_prev[row]) matrix_last_modified = timer_read32();
     }