[OpenMP][AArch64] Fix frame pointer save in microtask

[dominik-wojt-2311446]

When OMPT is enabled, the stack pointer was not saved to frame pointer register immediately after storing the frame pointer to the stack. Therefore the frame pointers did not constitute a proper chain.
Fixes #163352

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[MacDue]

LGTM, but I've tagged some reviewers who have worked on/reviewed OpenMP changes before.

[shiltian]

I don't really know the AArch64 asm very well, but I don't see any issue from OpenMP's perspective. Would be good to have some tests if possible.

[jprotze]

Running the ompt/tasks/task_types.c test should tell you whether the change broke something for OMPT:

LIT_FILTER=ompt/tasks/task_types.c make check-openmp
or
LIT_FILTER=ompt/tasks/task_types.c ninja check-openmp

If check-openmp cannot be found for a runtime build of openmp, you might need to go to BUILD/runtimes/runtimes-bin/ and start the test from there.