Switch NVDLA partition_o inter-clock SDC from set_false_path to set_clock_groups -asynchronous

[mguthaus]

Background

partition_o is the only NVDLA partition with two clocks: nvdla_core_clk (2000 ps) and nvdla_falcon_clk (2500 ps). The SDC that landed in #68 uses the closed-PR wording:

set_false_path -from [get_clocks nvdla_core_clk] -to [get_clocks nvdla_falcon_clk]
set_false_path -from [get_clocks nvdla_falcon_clk] -to [get_clocks nvdla_core_clk]

This passes end-to-end on Nautilus (15639 s to GDS), but the idiomatic form for asynchronous clock domains in OpenROAD's STA is:

set_clock_groups -asynchronous \
    -group [get_clocks nvdla_core_clk] \
    -group [get_clocks nvdla_falcon_clk]

set_clock_groups -asynchronous is a single declaration that disables timing between the groups in both directions. It's what CTS/STA look for to decide the clocks are asynchronous — the two set_false_path pairs are functionally equivalent for timing checks but don't always get interpreted the same way by clock-tree optimization.

Task

Swap partition_o's SDC over to set_clock_groups -asynchronous and confirm the flow still closes cleanly.

Acceptance

• bazel build //designs/asap7/NVDLA/partition_o:partition_o_final completes cleanly.
• Timing report shows the two clocks in separate asynchronous groups (not just flagged as false paths between each other).
• No QoR regression (runtime, area, timing, power within ~1% of baseline).

Related

• PR Add NVDLA nv_small partitions (a/c/m/o/p) on asap7 #68 (NVDLA port, current partition_o SDC)
• sdc-sta skill for SDC idiom reference.