As an attempt to stop issues with bad console output, ensure that both the
rx and tx interrupts are disabled during the console write to avoid any
problems with console and non-console being called together.

This should help with the SMP case as it should stop other cores being
signalled during the console write.
Signed-off-by: NBen Dooks <ben.dooks@codethink.co.uk>
Tested-by: NCarlo Caione <carlo@endlessm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>