Clean up AMD romstage.c serial output

Clean up AMD romstage.c serial output

This cleans up the strings in romstage.c, removing the ugly "got past".
Also, cleaned up comments and some spacing.

Change-Id: I0124df76eb442f8a0009a31a8632e4fd67ed7782
Signed-off-by: Marc Jones <marcj303@gmail.com>
Reviewed-on: http://review.coreboot.org/539
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>