earlycon: Revert log warnings

Log warnings meant to help diagnose problems setting up earlycon
are reporting false positives for 'console='. Revert to the
previous behavior which reported nothing.

Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Robert Schwebel <r.schwebel@pengutronix.de>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>