xen/arm: vgic-v3: message in the emulation code should be rate-limited

xen/arm: vgic-v3: message in the emulation code should be rate-limited

printk by default is not rate-limited by default. Therefore a malicious guest
may be able to flood the Xen console.

If we use gdprintk, unnecessary information will be printed such as the
filename and the line. Instead use XENLOG_G_{ERR,DEBUG} combine with %pv.

Also remove the vGICv3 prefix which is not neccessary and update some
message which were wrong.

This is XSA-118.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>