Fix for linker issue in AdBun-M066

[deepak-shreshti]

Summary of changes

Linker issue:
The hardcoded __initial_sp from the startup file of AdBun-M066 (startup_TMPM066.S) has been removed.
The initial stack pointer value ARM_LIB_STACK has been imported from the scatter file of AdBun-M066 (tmpm066fwug.sct).

As per scatter file of AdBun-M066,
initial stack pointer = 0x200000C0 + 0x4000 : 0x200040C0 (which is beyond the RAM of AdBun-M066)

So, Stack pointer must be initialized to =
RAM starting address + Size of RAM = 0x20000000 + 0x4000 (16KB)

Impact of changes

Migration actions required

Documentation

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Pull request type

[x] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[ ] Feature update (New feature / Functionality change / New API)
[ ] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[x] No Tests required for this change (E.g docs only update)
[ ] Covered by existing mbed-os tests (Greentea or Unittest)
[ ] Tests / results supplied as part of this PR

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Reviewers

@0xc0170

[ciarmcom]

@deepak-shreshti, thank you for your changes.
@0xc0170 @ARMmbed/mbed-os-maintainers please review.

[0xc0170]

We will start CI after we complete the next 6.x release (or if the CI queue allows, earlier).

[0xc0170]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 10 of 10 test jobs passed
Build number : 1
Build artifacts

[andypowers]

Approved.