i2c: tegra: allow VI support to be compiled out

Save a bit of code for older Tegra platforms by compiling out
VI's I2C mode support that's used only for Tegra210.

$ size i2c-tegra.o
   text    data     bss     dec     hex filename
  11381     292       8   11681    2da1 i2c-tegra.o (full)
  10193     292       8   10493    28fd i2c-tegra.o (no-dvc)
   9145     292       8    9445    24e5 i2c-tegra.o (no-vi,no-dvc)

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>