mx6sabresd: Fix IOMUXC_GPR6 and IOMUXC_GPR7 values

The IPU AXI QoS for the i.MX6QP and i.MX6DP processors have to be set as
commented in the code:
/* set IPU AXI-id1 Qos=0x1 AXI-id0/2/3 Qos=0x7 */

Set IOMUXC_GPR6 and IOMUXC_GPR7 to 0x77177717 instead of 0x007F007F.

Signed-off-by: Breno Lima <breno.lima@nxp.com>