Set CI tag to libero-soc-v2023.2 to execute CI on gitlab runners using version
2023.2 of Libero.

Correct the location of the gateware source code in the script that
generates the device tree overlay for the gateware.

The build configuration YAML files describing a custom gateware
configuration will be used by the CI system generate bitstreams for user
custom FPGA designs.

First argument removed from gateware-builds-tester script.

The intention is to replace GATEWARE_GIT_VERSION within the "chosen" section
of the device tree overlay with git hash/branch/tag gateware
repository information to help identify the gateware version at
run time.

Allow the control of M2_UART_RTS and M2_UART_CTS from the CorePGIO
instance used for board tests of the M.2 connector.

This makes it easier to figure out from Linux which gateware functionalities are
included.

Without the dtso, the default Linux dts for MSS GPIO2 is used causing
non-connected P8 pins being reported as usable.

This is requrired to help seeing boot and reprogramming progress.

Temporary switch to Platinum license for CI.

- Correct the number of gpios and gpio controller's base address in dts.
- Loopback the gpios outputs to the inputs so that the output values is
read back from software (avoids the outputs looking like they are not
working).