drm/amd/display: Use 16ms AUX read interval for LTTPR with old sinks

[Why/How]
LTTPR are required to program DPCD 0000Eh to 0x4 (16ms) upon AUX read
reply to this register. Since old Sinks witih DPCD rev 1.1 and earlier
may not support this register, assume the mandatory value is programmed
by the LTTPR to avoid AUX timeout issues.

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Signed-off-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Tested-by: Mark Broadworth <mark.broadworth@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 1594b60d)