hw/intc/arm_gic: Un-inline GIC*/ITS class_name() helpers

hw/intc/arm_gic: Un-inline GIC*/ITS class_name() helpers

"kvm_arm.h" contains external and internal prototype declarations.
Files under the hw/ directory should only access the KVM external
API.

In order to avoid machine / device models to include "kvm_arm.h"
simply to get the QOM GIC/ITS class name, un-inline each class
name getter to the proper device model file.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230405160454.97436-4-philmd@linaro.org>