ti: k3: common: Make UART number configurable

This allows to build for k3-based boards that use a different UART as
console, such as the IOT2050 which requires K3_USART=1.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Change-Id: I7171f86c3cabae2c575b8fbeecef839b48bd109b
2 files changed