powerpc/eeh: Introduce eeh_edev_actionable()

The same test is done in every EEH report function, so factor it out.

Since eeh_dev_removed() needs to be moved higher up in the file,
simplify it a little while we're at it.

Signed-off-by: Sam Bobroff <sbobroff@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>