arm64: don't create a section for z_arm64_exit_exc_fpu_done
arm64: don't create a section for z_arm64_exit_exc_fpu_done

Both z_arm64_exit_exc and z_arm64_exit_exc_fpu_done must be within
the same section as execution falls through here.

If z_arm64_exit_exc_fpu_done creates a section of its own then the
linker is free to disjoint the code and we absolutely don't want that.

Signed-off-by: Nicolas Pitre <76342682d5afc62854e1102d9578521fe1ed6813@baylibre.com>

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