Extensible split data sync (#11930)

* Extensible split data sync capability through transactions.

- Split common transport has been split up between the transport layer
  and data layer.
- Split "transactions" model used, with convergence between I2C and
  serial data definitions.
- Slave matrix "generation count" is used to determine if the full slave
  matrix needs to be retrieved.
- Encoders get the same "generation count" treatment.
- All other blocks of data are synchronised when a change is detected.
- All transmissions have a globally-configurable deadline before a
  transmission is forced (`FORCED_SYNC_THROTTLE_MS`, default 100ms).
- Added atomicity for all core-synced data, preventing partial updates
- Added retries to AVR i2c_master's i2c_start, to minimise the number of
  failed transactions when interrupts are disabled on the slave due to
  atomicity checks.
- Some keyboards have had slight modifications made in order to ensure
  that they still build due to firmware size restrictions.

* Fixup LED_MATRIX compile.

* Parameterise ERROR_DISCONNECT_COUNT.

1 files changed, 2 insertions, 0 deletions

diff --git a/keyboards/keebio/iris/rev4/rules.mk b/keyboards/keebio/iris/rev4/rules.mk
index ea92bc98f5..9bf5688da0 100644
--- a/keyboards/keebio/iris/rev4/rules.mk
+++ b/keyboards/keebio/iris/rev4/rules.mk
@@ -33,3 +33,5 @@ SLEEP_LED_ENABLE = no    # Breathing sleep LED during USB suspend
 
 SPLIT_KEYBOARD = yes
 ENCODER_ENABLE = yes
+
+LTO_ENABLE = yes
\ No newline at end of file