arm: Add CONFIG_DISPLAY_BOARDINFO_LATE to display board info on LCD

This option displays board info after stdio is running, so that it will
appear on the LCD. If it is displayed earlier, the board info will appear
on the serial console but not on the LCD.

Here follows a blow-by-blow description.

1a. Without CONFIG_DISPLAY_BOARDINFO_LATE, on serial:

U-Boot 2011.12-02550-g037e1c5-dirty (Nov 15 2012 - 14:29:42) for SMDK5250

CPU:   S5PC520 @ 1700MHz

Board: Google Snow, rev 0
I2C:   ready
DRAM:  2 GiB Elpida DDR3 @ 800MHz
MMC:   S5P MSHC0: 0, S5P MSHC1: 1
SF: Detected W25Q32 with page size 4 KiB, total 4 MiB
*** Warning - bad CRC, using default environment

In:    mkbp-keyb
Out:   lcd
Err:   lcd
Net:   No ethernet found.
Hit any key to stop autoboot:  0
SMDK5250 #

1b. Without CONFIG_DISPLAY_BOARDINFO_LATE, on LCD (note machine info
is missing):

In:    mkbp-keyb
Out:   lcd
Err:   lcd
Net:   No ethernet found.
Hit any key to stop autoboot:  0
SMDK5250 #

2a. With CONFIG_DISPLAY_BOARDINFO_LATE, on serial:

U-Boot 2011.12-02550-g037e1c5 (Nov 15 2012 - 14:27:40) for SMDK5250

CPU:   S5PC520 @ 1700MHz
I2C:   ready
DRAM:  2 GiB Elpida DDR3 @ 800MHz
MMC:   S5P MSHC0: 0, S5P MSHC1: 1
SF: Detected W25Q32 with page size 4 KiB, total 4 MiB
*** Warning - bad CRC, using default environment

Model: Google Snow
In:    mkbp-keyb
Out:   lcd
Err:   lcd
Net:   No ethernet found.
Hit any key to stop autoboot:  0
SMDK5250 #

2b. With CONFIG_DISPLAY_BOARDINFO_LATE, on LCD (note machine info is present):

Model: Google Snow
In:    mkbp-keyb
Out:   lcd
Err:   lcd
Net:   No ethernet found.
Hit any key to stop autoboot:  0
SMDK5250 #

Since the LCD is all that a typical user sees, it is useful to display
the model there.

We may be able to rearrange things some other way one day, but at
present this seems like a convenient way of getting the required
behaviour.

Signed-off-by: Simon Glass <sjg@chromium.org>