By setting CONFIG_DEBUG, the native_posix builds will not be optimized
which makes debugging them much nicer.
By setting CONFIG_SYS_CLOCK_TICKS_PER_SEC to 1000, debug prints have a
higher resolution and not always show up as multiples of 10ms.
* For now, to be used for FrankenKyria, where both
matrix halves will be attached to the same MCU, but
should be a stepping stone to proper split support
once we have a kscan driver over a split transport.
* Implement multiple instances for mock kscan driver.
Alessandro Bortolin