devel/llvm-cheriot: fix plist for EXTRAAS

This should have been updated as part of the commit below and the
PORTREVISION bump did apply to all. I was working on two things related
to these ports (one of which didn't touch llvm-cheriot) and got mixed
up.

Reported by: jrtc27
Fixes: f7f5f916e676 devel/llvm-{cheri,morello}: add clang-tools-extras