arm: Use .data.rel.ro for const data with relocations

Signed-off-by: Martin Storsjö <martin@martin.st>
aarch64: Use .data.rel.ro for const data with relocations

This reverts commit c00365b46d464ce47716315c1801818d811bdb9a
in addition to using a different section.

Signed-off-by: Martin Storsjö <martin@martin.st>