util: Add missing iostream header to util/m5/src/commands.cc
util: Add missing iostream header to util/m5/src/commands.cc

Signed-off-by: Hoa Nguyen <a0aa8449aacb303edcb25d6bbe69da9124f010fc@ucdavis.edu>
Change-Id: I93f99284ecda22c73572cc0ffa8c3be0160ce560
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/30734
Reviewed-by: Jason Lowe-Power <92de577f37050ad05b60626d2f17913f40dcb1a2@gmail.com>
Reviewed-by: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>
Maintainer: Jason Lowe-Power <92de577f37050ad05b60626d2f17913f40dcb1a2@gmail.com>
Maintainer: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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