Enhanced Error Handling could mean anything in the context of the entire
kernel, so change the name to reference that it is both for PCI and
powerpc.

EEH covers a bit more than the previously listed files, so add the headers
and platform-specific code to the EEH maintained section.

In addition, I am taking over the maintainership.
Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>