Improvements to handling of disconnected split keyboards. (#14033)
* Use memcmp and memcpy to compare and copy slave matrix.
...and memset to initialize `matrix` and `raw_matrix`.
Increased my scan rate (while connected) by ~100 (on Ergodox Infinity).
Effect on AVR is unknown.
Co-authored-by: Stefan Kerkmann <karlk90@pm.me>
* Fix `matrix_post_scan` signalling change on every scan while disconnected.
* Undo removal of initialization of `slave_matrix`.
This has the effect of increasing my Ergodox Infinity firmware size by 8
bytes instead of decreasing by 8 bytes, and lowers the scan rate while
connected back to the initial value before these changes, but _might_
solve some issues on AVR.
Co-authored-by: Stefan Kerkmann <karlk90@pm.me>