system: fix comment of file name

galileo.c currently calls itself system.c in a comment.  It lies.
ia32.c currently calls itself system.c in a comment. Don't believe it.
ia32_pci.c currently calls itself system.c in a comment.  It lies.

Change-Id: Icdba074ff2e2e478529bc5757c90b5adbc9dcb8a
Signed-off-by: Dan Kalowsky <daniel.kalowsky@intel.com>