bootcount: store bootcount var in environment

If no softreset save registers are found on the hardware
"bootcount" is stored in the environment. To prevent a
saveenv on all reboots, the environment variable
"upgrade_available" is introduced. If "upgrade_available" is
0, "bootcount" is always 0 therefore no need to save the
environment on u-boot boot, if "upgrade_available" is 1 "bootcount"
is incremented in the environment and environment gets written
on u-boot start.
So the Userspace Applikation must set the "upgrade_available"
and "bootcount" variable to 0 (for example with fw_setenv),
if a boot was successfully.

Signed-off-by: Heiko Schocher <hs@denx.de>
arm, am335x: add boutcount feature for the siemens boards

store the bootcount in the environment, as we have no softreset
save registers on this hardware. Use therefore the CONFIG_BOOTCOUNT_ENV
bootcount driver.

Signed-off-by: Heiko Schocher <hs@denx.de>
arm, am335x: adapt environment for bootcount feature

Signed-off-by: Heiko Schocher <hs@denx.de>
arm, am335x: add altbootcmd to default environment

Signed-off-by: Heiko Schocher <hs@denx.de>
i2c, omap24xx: convert driver to new mutlibus/mutliadapter framework

- add omap24xx driver to new multibus/multiadpater support
- adapted all config files, which uses this driver

Tested on the am335x based siemens boards rut, dxr2 and pxm2
posted here:
http://patchwork.ozlabs.org/patch/263211/

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Tom Rini <trini@ti.com>
Cc: Lars Poeschel <poeschel@lemonage.de>
Cc: Steve Sakoman <sakoman@gmail.com>
Cc: Thomas Weber <weber@corscience.de>
Cc: Tom Rix <Tom.Rix@windriver.com>
Cc: Grazvydas Ignotas <notasas@gmail.com>
Cc: Enric Balletbo i Serra <eballetbo@iseebcn.com>
Cc: Luca Ceresoli <luca.ceresoli@comelit.it>
Cc: Igor Grinberg <grinberg@compulab.co.il>
Cc: Ilya Yanok <yanok@emcraft.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Nishanth Menon <nm@ti.com>
Cc: Pali Rohár <pali.rohar@gmail.com>
Cc: Peter Barada <peter.barada@logicpd.com>
Cc: Nagendra T S  <nagendra@mistralsolutions.com>
Cc: Michael Jones <michael.jones@matrix-vision.de>
Cc: Raphael Assenat <raph@8d.com>

***
- changes for v2:
  rebased against u-boot-ti 425faf74cd8189c87919f7e72a0101c684ee3b9f
- changes for v3:
  rebase against: u-boot-it 901ce27c6f018992b7dd6c08d3c98cf217cc4c96
  add siemens boards (rut, dxr2 and pxm2)