kern/59233: patch to soundcard.h to include an ioctl and a constant for midi

[Mathew Kanner]

Hello All,
	I'm sorry to be a pain, but I think it's important this PR be
commited before any branch.  
	http://www.freebsd.org/cgi/query-pr.cgi?pr=59233
	It's vital to build current midi software and it has been in
other OSes for a while.

	Thanks,

	--Mat