Add conditional definition for SW_SERIAL_UART

[jrhuerta]

Define SW_SERIAL_UART if not already defined.
Avoid warnings when configuring ramps board to use Serial3 for TMC2209 drivers in UART mode in Configuration_local.hpp

#define SW_SERIAL_UART 0
#define RA_SERIAL_PORT Serial3
#define RA_DRIVER_ADDRESS 0b00
#define DEC_SERIAL_PORT Serial3
#define DEC_DRIVER_ADDRESS 0b01

[ClutchplateDude]

LGTM

[jrhuerta]

Thanks for taking a look at this PR.

I noticed the changelog check is failing. I’ve seen cases where updates are bundled and the version is bumped afterward, please let me know if there’s anything I should address on my side, or if I should just wait.

[ClutchplateDude]

Yeah, generally, PRs require a version update and a changelog update.... But with such trivial changes, I think we can circumvent that rule...