scx_lavd: Use time_delta() for clock difference calculation #5807

Job	Run time
lint	13s
build-kernel	13s
pages	0s
rust-test-schedulers (scx_bpfland)	9m 36s
layered-matrix (scx_layered, --disable-topology=false)	2m 50s
rust-test-schedulers (scx_lavd)	10m 22s
integration-test (scx_bpfland)	4m 12s
layered-matrix (scx_layered, --disable-topology=false, --disable-antistall)	2m 49s
rust-test-schedulers (scx_layered)	9m 8s
rust-test-core (scx_loader)	5m 3s
integration-test (scx_lavd)	4m 23s
layered-matrix (scx_layered, --disable-topology=true)	2m 38s
rust-test-schedulers (scx_rlfifo)	10m 7s
rust-test-core (scx_rustland_core)	8m 1s
integration-test (scx_layered)	3m 45s
layered-matrix (scx_layered, --disable-topology=true, --disable-antistall)	3m 31s
rust-test-schedulers (scx_rustland)	11m 8s
rust-test-core (scx_stats)	3m 43s
integration-test (scx_rlfifo)	2m 56s
rust-test-schedulers (scx_rusty)	9m 5s
rust-test-core (scx_utils)	9m 35s
integration-test (scx_rustland)	3m 23s
integration-test (scx_rusty)	4m 1s
	2h 0m 42s

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