i2c: Let users select algorithm drivers manually again

In kernel 2.6.26, the ability to select I2C algorithm drivers manually
was removed, as all in-kernel drivers do that automatically. However
there were some complaints that it was a problem for out-of-tree I2C
bus drivers. In order to address these complaints, let's allow manual
selection of these drivers again, but still hide them by default for
better general user experience.

This closes bug #11140:
http://bugzilla.kernel.org/show_bug.cgi?id=11140

Signed-off-by: Jean Delvare <khali@linux-fr.org>