MN10300: Change "Matsushita" to "Panasonic".

Change externally visible "Matsushita" instances to "Panasonic" throughout the
MN10300 arch code.

Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Signed-off-by: David Howells <dhowells@redhat.com>