ARM: tegra: board2: add generic late init

ARM: tegra: board2: add generic late init

Board specific late init allows vendors to set up different device
or board specific env variables (like serial number, platform name).
In case this information is missing, u-boot will lack info regards
serial or platform.

To avoid this prior nvidia_board_late_init internal generic function
is called which fills required data. In this case platform name is
obtained from get_chip and serialno is filled with SoC id.

Though SoC id is not dedicated to be devices serial but it fits well
in case of restriction of data about device and since SoC is basically
a main chip of the device.

Tested-by: Andreas Westman Dorcsak <hedmoo@yahoo.com> # ASUS Transformers
Tested-by: Svyatoslav Ryhel <clamor95@gmail.com> # Nvidia Tegratab
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>