Almost all thunks are already ARMv5 safe, so we can just require this
architecture on the gas command line, to enforce compatibility with the
F1Cx00 series. This prevents accidental changes in the future.
The RMR thunk uses the ARMv7 only DSB/ISB instructions, but this runs on
ARMv8 cores only anyway, so we just force ARMv7 for this file, and avoid
code changes.
Signed-off-by: Andre Przywara <osp@andrep.de>
