i2c: Use pci_ioremap_bar()

Use the newly introduced pci_ioremap_bar() function in drivers/i2c.
pci_ioremap_bar() just takes a pci device and a bar number, with the goal
of making it really hard to get wrong, while also having a central place
to stick sanity checks.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>