drm/arm/mali-dp: Add display QoS interface configuration for Mali DP500

Configure the display Quality of service (QoS) levels priority if the
optional property node "arm,malidp-aqros-value" is defined in DTS file.

QoS signaling using AQROS and AWQOS AXI interface signals, the AQROS is
driven from the "RQOS" register, so needed to program the RQOS register
to avoid the high resolutions flicker issue on the LS1028A platform.

Signed-off-by: Wen He <wen.he_1@nxp.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190910075913.17650-2-wen.he_1@nxp.com