Document ARC specific syscalls/splice02 invocation change

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
for upstream: fix usage of mtest07/mallocstress

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Re-enable mm/mallocstress01 for ARC with reduced iters

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>