i2c: designware: Combine some of the common functions

i2c: designware: Combine some of the common functions

The adapter can be registered just in the core instead of
separately in the master and slave drivers. The same applies
to the interrupt.

The dedicated "target only" (slave only) configuration
for this controller will be removed so that host mode
(master mode) will always be supported together with the
target mode. Therefore the descrption for the "target only"
configuration that appears in the "name" sysfs attribute
file is also dropped while at it.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260120130729.1679560-2-heikki.krogerus@linux.intel.com