firmware: arm_scmi: Report duplicate opps as firmware bugs

Duplicate opps reported by buggy SCP firmware currently show up
as warnings even though the only functional impact is that the
level/index remain inaccessible. Make it less scary for the end
user by using dev_info instead, along with FW_BUG tag.

Suggested-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Cc: stable@vger.kernel.org
Message-ID: <20241030125512.2884761-4-quic_sibis@quicinc.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>