arm64: stacktrace: restore terminal records

We removed the terminal frame records in commit:

   6106e1112cc69a36 ("arm64: remove EL0 exception frame record")

... on the assumption that as we no longer used them to find the pt_regs
at exception boundaries, they were no longer necessary.

However, Leo reports that as an unintended side-effect, this causes
traces which cross secondary_start_kernel to terminate one entry too
late, with a spurious "0" entry.

There are a few ways we could sovle this, but as we're planning to use
terminal records for RELIABLE_STACKTRACE, let's revert the logic change
for now, keeping the update comments and accounting for the changes in
commit:

  3c02600144bdb0a1 ("arm64: stacktrace: Report when we reach the end of the stack")

This is effectively a partial revert of commit:

  6106e1112cc69a36 ("arm64: remove EL0 exception frame record")

Signed-off-by: Mark Rutland <[email protected]>
Fixes: 6106e1112cc6 ("arm64: remove EL0 exception frame record")
Reported-by: Leo Yan <[email protected]>
Tested-by: Leo Yan <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Mark Brown <[email protected]>
Cc: "Madhavan T. Venkataraman" <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Catalin Marinas <[email protected]>

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