i3c: support dynamically added i2c devices

I2C devices can be added to the system dynamically through several
sources other than static board info including device tree overlays and
sysfs i2c new_device.

Add an I2C bus notifier to attach the clients at runtime if they were
not defined in the board info.  For DT devices find the LVR in the reg
property, for user-space new_device additions we synthesize a
conservative setting of no spike filters and fast mode only.

Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Jamie Iles <quic_jiles@quicinc.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220117174816.1963463-3-quic_jiles@quicinc.com