drm/amd/display: Fix out-of-bounds read in dp_get_eq_aux_rd_interval()

drm/amd/display: Fix out-of-bounds read in dp_get_eq_aux_rd_interval()

[Why & How]
The aux_rd_interval array in struct dc_lttpr_caps is declared with
MAX_REPEATER_CNT - 1 (7) elements, indexed 0..6. However, the offset
parameter passed to dp_get_eq_aux_rd_interval() can be as large as
MAX_REPEATER_CNT (8) when a sink reports 8 LTTPR repeaters via DPCD.
This leads to an out-of-bounds read of aux_rd_interval[7] when offset
is 8.

Fix this by growing aux_rd_interval to MAX_REPEATER_CNT elements to
accommodate the full range of valid repeater counts defined by the DP
spec.

Assisted-by: GitHub Copilot:Claude claude-4-opus
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit a55a458a8df37a65ffda5cf721d554a8f74f6b04)
Cc: stable@vger.kernel.org