i3c: add sysfs entry and attribute for Device NACK Retry count

i3c: add sysfs entry and attribute for Device NACK Retry count

Document sysfs attribute dev_nack_retry_cnt that controls the number of
automatic retries performed by the I3C controller when a target device
returns a NACK

Add a `dev_nack_retry_count` sysfs attribute to allow reading and updating
the device NACK retry count. A new `dev_nack_retry_count` field and an
optional `set_dev_nack_retry()` callback are added to
i3c_master_controller. The attribute is created only when the callback is
implemented.

Updates are applied under the I3C bus maintenance lock to ensure safe
hardware reconfiguration.

Signed-off-by: Adrian Ng Ho Yin <adrianhoyin.ng@altera.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/3c4b5082bde64024fc383c44bebeef89ad3c7ed3.1765529948.git.adrianhoyin.ng@altera.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>