powerpc/eeh: Cleanup list_head field names

Instances of struct eeh_pe are placed in a tree structure using the
fields "child_list" and "child", so place these next to each other
in the definition.

The field "child" is a list entry, so remove the unnecessary and
misleading use of the list initializer, LIST_HEAD(), on it.

The eeh_dev struct contains two list entry fields, called "list" and
"rmv_list". Rename them to "entry" and "rmv_entry" and, as above, stop
initializing them with LIST_HEAD().

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