The official punctuation for Arm CPU names uses a hyphen, like
"Cortex-A9". We mostly follow this, but in a few places usage
without the hyphen has crept in. Fix those so we consistently
use the same way of writing the CPU name.

This commit was created with:
  git grep -z -l 'Cortex ' | xargs -0 sed -i 's/Cortex /Cortex-/'

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20210527095152.10968-1-peter.maydell@linaro.org