i2c-pca-isa: Add access check to legacy ioports

When probing i2c-pca-isa writes to legacy ioports, which crashes the kernel
if there is no device at that port.
This patch adds a check_legacy_ioport call, so probe fails gracefully
and thus prevents the oops.

Signed-off-by: Christian Krafft <krafft@de.ibm.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>