Debian does not ship a 'mkisofs' symlink to genisoimage.  All modern
distros ship genisoimage, so just use that directly.  That requires
renaming the 'genisoimage' function.  Also neaten up the 'for' loop
while I'm in here.
Signed-off-by: NMatthew Wilcox <mawilcox@microsoft.com>
Cc: Changbin Du <changbin.du@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>