ARM: dts: n900: fix i2c bus numbering

With legacy boot i2c buses on Nokia N900 are numbered i2c1, i2c2 and i2c3.
Commit 20b80942

 ("ARM: dts: OMAP3+: Add i2c aliases") fixed the
numbering with DT boot, but introduced a regression on N900 - aliases
become i2c0, i2c1 and i2c2. Fix that by providing the correct aliases in
the board dts.

Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Tested-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Nishanth Menon <nm@ti.com>
[tony@atomide.com: this is needed for legacy user space to work]
Signed-off-by: Tony Lindgren <tony@atomide.com>