armv7a9-qemu: Adjust serial device

[maska989]

JIRA: CI-397

Description

In the process of creating a test that check's Control Codes, there is a problem with our QEMU setup.
qemu-system-aarch64 with machine arm-generic-fdt-7series have multiple serials outputs. First one is responsible for VNC connection. Second one is strictly connected with emulated environment. Redirecting it to mon:stdio give us access to use QEMU shortcuts which they collide with our tests. Even in further use cases, this will be a problem.
Shortcuts available with serial output set on to mon:stdio:

To minimize interference from QEMU side, we can simply redirect serial directly on stdio and solve this problem.

Motivation and Context

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

How Has This Been Tested?

• Already covered by automatic testing.
• New test added: (add PR link here).
• Tested by hand on: armv7a9-zynq7000-qemu.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (list the PRs, preferably in merge-order).
• I will merge this PR by myself when appropriate.

[github-actions]

Unit Test Results

7 460 tests  +890   6 745 ✅ +801   37m 10s ⏱️ + 5m 23s
  420 suites + 54     715 💤 + 89 
    1 files   ±  0       0 ❌ ±  0 

Results for commit 95f723f. ± Comparison against base commit 146f024.

♻️ This comment has been updated with latest results.

[nalajcie]

IMHO this is desirable only when running automatic tests, either make a separate script or depend on external parameter / env variable to disable monitor.

[maska989]

@nalajcie Thanks for perfect advice. Added new pr on phoenix-rtos-test submodule to utilize this change. This will impact less for people using QEMU as they desired.