of: Fix comparison of "compatible" properties

Commit 7c7b60cb
"of: put default string compare and #a/s-cell values into common header"

Breaks various things on powerpc due to using strncasecmp instead of
strcasecmp for comparing against "compatible" strings.

This causes things like the 4xx PCI code to fail miserably due to the
partial matches in code like this:

       for_each_compatible_node(np, NULL, "ibm,plb-pcix")
               ppc4xx_probe_pcix_bridge(np);
       for_each_compatible_node(np, NULL, "ibm,plb-pci")
               ppc4xx_probe_pci_bridge(np);

It's not quite right to do partial name match. Entries in a compatible
list are meant to be matched whole. If a device is compatible with both
"foo" and "foo1", then the device should have both strings in its
"compatible" property.

This patch reverts powerpc and microblaze us to use strcasecmp.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
      (for patch description)
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Simek <michal.simek@petalogix.com>