firewire: revert to 4 GB RDMA, fix protocols using Memory Space

Undo a feature introduced in v3.14 by commit fcd46b34
"firewire: Enable remote DMA above 4 GB".  That change raised the
minimum address at which protocol drivers and user programs can register
for request reception from 0x0001'0000'0000 to 0x8000'0000'0000.
It turned out that at least one vendor-specific protocol exists which
uses lower addresses:  https://bugzilla.kernel.org/show_bug.cgi?id=76921



For the time being, revert most of commit fcd46b34 so that affected
protocols work like with kernel v3.13 and before.  Just keep the valid
documentation parts from the regressing commit, and the ability to
identify controllers which could be programmed to accept >32 bit
physical DMA addresses.  The rest of fcd46b34 should probably be
brought back as an optional instead of default feature.

Reported-by: Fabien Spindler <fabien.spindler@inria.fr>
Cc: <stable@vger.kernel.org> # 3.14+
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>