Please support "-soundhw none"

qemu currently provides a default set of sound hardware.  The -soundhw option can change that default set, such as by using "-soundhw pcspkr" to disable most of it, but no "-soundhw none" option exists to disable all of it.  As far as I can tell, disabling the default sound hardware requires specifying -nodefaults and then manually specifying all the desired hardware, leaving out sound hardware.

Please consider adding support for "-soundhw none", to disable all the default sound hardware.