openrisc: rename or32 code & comments to or1k

From Documentation/openrisc/todo.rst, rename "or32" in the
source code to "or1k" since this is the name that has been
settled on.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Stafford Horne <shorne@gmail.com>
Cc: openrisc@lists.librecores.org
Signed-off-by: Stafford Horne <shorne@gmail.com>