MAINTAINERS: ARM/VT8500, remove defunct e-mail

linux@prisktech.co.nz is defunct:

  4.1.2 <linux@prisktech.co.nz>: Recipient address rejected: Domain not found

Remove it from MAINTAINERS and mark the ARM/VT8500 entry orphan.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>