tty: serial: lpc32xx_hs: fix missing console boot messages

When probing the HSUART, it is put in loopback mode in order to prevent a
potential issue that may happen on RX (Errata HSUART.1).

serial_lpc32xx_startup() moves it out of loopback mode but this is too late
to get the kernel boot messages before userspace opens the device.

Also get out of loopback mode in lpc32xx_hsuart_console_setup().

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>