ARM: omap2plus_defconfig: Fix probe errors on UARTs 5 and 6

[ Upstream commit 4cd6a59f5c1a9b0cca0da09fbba42b9450ffc899 ]

We have more than four uarts on some SoCs and that can cause
noise with errors while booting.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>