unicore32: standardize /proc/iomem "Kernel code" name

All other ports use "Kernel code" to identify the Kernel text segment
in /proc/iomem. Change the unicore32 resources to do the same.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>