Convert 2420 platform init code to use new mux code
Signed-off-by: NTony Lindgren <tony@atomide.com>

The commit b63128e8 broke the pin muxing
for I2C busses that are enabled from the kernel command line.

Fix this by defining the board registration function omap_register_i2c_bus
in common platform code as it was before but keep the muxing in architecture
dependent files.
Signed-off-by: NJarkko Nikula <jhnikula@gmail.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>

Otherwise we cannot limit new mux code to mach-omap2.
The same signal names should eventually work for other
omaps under mach-omap2.

Note that these pins don't need to be OMAP_PIN_INPUT_PULLUP,
just OMAP_PIN_INPUT is enough.

Cc: Jarkko Nikula <jhnikula@gmail.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>