kpb: Increase number of supported clients to 4 #255

Job	Run time
manifest-check	3m 7s
build-windows (imx8 imx8x imx8m imx8ulp)	14m 45s
build-windows (mtl lnl)	13m 56s
LP64-WIP	4m 38s
build-windows (-d, lnl)	10m 13s
build-windows (tgl tgl-h)	11m 26s
build-windows (ptl)	8m 27s
build-linux (mnfst, mtl lnl)	6m 20s
build-linux (mnfst, ptl)	4m 45s
build-linux (mnfst, imx8 imx8x imx8m imx8ulp)	7m 4s
build-linux (mnfst, --all)	17m 34s
build-linux (-d, mnfst, lnl)	4m 53s
build-linux (zmain, ptl)	5m 5s
build-linux (zmain, imx8 imx8x imx8m imx8ulp)	4m 1s
build-linux (mnfst, tgl tgl-h)	6m 1s
build-linux (zmain, mtl lnl)	4m 49s
build-linux (zmain, tgl tgl-h)	4m 25s
compare-linux-win	32s
	2h 12m 1s

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