drm/amd/display: update sr latency for renoir when using lpddr4

[Why]
DF team has produced more optimized sr latency numbers, for lpddr4

[How]
change the sr laency in the lpddr4 wm table to the new latency
number

Signed-off-by: Joseph Gravenor <joseph.gravenor@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>