i2c: pasemi: Split pci driver to its own file

Split off the PCI driver so that we can reuse common code for the
platform driver.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Acked-by: Olof Johansson <olof@lixom.net>
Tested-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>