phy: fsl-imx8mq-usb: fix tuning parameter name

According to fsl,imx8mq-usb-phy.yaml, this tuning parameter should be
fsl,phy-pcs-tx-deemph-3p5db-attenuation-db.

Fixes: 63c85ad0 ("phy: fsl-imx8mp-usb: add support for phy tuning")
Cc: stable@vger.kernel.org
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Link: https://lore.kernel.org/r/20240801124642.1152838-1-xu.yang_2@nxp.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>