Convert string compares of DT node names to use of_node_name_{eq,prefix}
helpers instead. This removes direct access to the node name pointer.

This changes a single case insensitive node name comparison to case
sensitive for "ata4". This is the only instance of a case insensitive
comparison for all the open coded node name comparisons on powerpc.
Searching the commit history, there doesn't appear to be any reason for
it to be case insensitive.

A couple of open coded iterating thru the child node names are converted
to use for_each_child_of_node() instead.
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>