ARM: Clarifies creation of Linux and baremetal ARM systems.

ARM: Clarifies creation of Linux and baremetal ARM systems.

makeArmSystem creates both bare-metal and Linux systems more cleanly.
machine_type was never optional though listed as an optional argument; a system
such as "RealView_PBX" must now be explicitly specified.  Now that it is a
required argument, the placement of the arguments has changed slightly
requiring some changes to calls that create ARM systems.