Fixes the crippled console output on PortuxG20.

Fixes the crippled console output on PortuxG20.

In order to use the serial interface on the PortuxG20 we need to enable the
level converter first by setting the PC9 pin to high. The level converter needs
some time to settle so we have to use the mdelay() function to wait for some
time. Unfortunately we have no timers available at board_early_init_f() so we
enable the serial output early within board_postclk_init().

Now the U-Boot output looks fine:

| U-Boot 2012.07-00132-gaf1a3b0-dirty (Aug 16 2012 - 18:21:32)
|
| CPU: AT91SAM9G20
| Crystal frequency:   18.432 MHz
| CPU clock        :  396.288 MHz
| Master clock     :  132.096 MHz
| DRAM:  64 MiB
| WARNING: Caches not enabled
| NAND:  128 MiB
| In:    serial
| Out:   serial
| Err:   serial
| Net:   macb0
| Hit any key to stop autoboot:  0

Signed-off-by: Markus Hubig <mhubig@imko.de>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>