SAMPLES: shell_module gives no console output on qemu_leon3

[ghost]

Describe the bug
There is no console input or output when running the shell_module sample on the qemu_leon3 board.
Also reproduced on the board generic_leon3.

To Reproduce
Steps to reproduce the behavior:

1. cmake $ZEPHYR_BASE/samples/subsys/shell/shell_module -DBOARD=qemu_leon3
2. make
3. make run

Expected behavior
It was expected that the program would print the shell prompt and accept commands.

Actual behavior
The program did not print the shell prompt and did not respond to commands.

Impact
The shell can not be used.

Environment (please complete the following information):

• OS: Linux
• Toolchain: Zephyr-SDK 0.12.
• Commit: 94e8c2eb81f390a9226a3b70fdb69a002642f274

Additional context
The UART driver otherwise works, for example in other samples.