i2c: designware: Implement I2C_M_STOP support

i2c: designware: Implement I2C_M_STOP support

Add the support of the I2C_M_STOP flag in i2c_msg by splitting
i2c_dw_xfer() in two: __i2c_dw_xfer_one_part() for the core transfer logic
and i2c_dw_xfer() for handling the high-level transaction management.

In detail __i2c_dw_xfer_one_part() starts a transaction and wait for its
completion, either with a STOP on the bus or an error. i2c_dw_xfer()
loops over the messages to search for the I2C_M_STOP flag and calls
__i2c_dw_xfer_one_part() for each part of the messages up to a STOP or
the end of the messages array.

i2c_dw_xfer() takes care of runtime PM and holds the hardware lock on
the bus while calling __i2c_dw_xfer_one_part(), this allows grouping
multiple accesses to device that support a STOP in a transaction when
done via i2c_dev I2C_RDWR ioctl.

Also, now that we have a lookup of the messages in i2c_dw_xfer() prior
to each transaction, we use it to make sure the messages are valid for
the transaction, via a new function i2c_dw_msg_is_valid(). We check
that the target address does not change before starting the transaction
instead of aborting the transfer while it is happening, as it was done
in i2c_dw_xfer_msg(). The target address can only be changed after an
I2C_M_STOP flag, i.e after a STOP on the i2c bus.

The I2C_FUNC_PROTOCOL_MANGLING flag is added to the list of
functionalities supported by the controller, except for the AMD NAVI
i2c controller which uses its own xfer() function and is left untouched.

Signed-off-by: Benoît Monin <benoit.monin@bootlin.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260130-i2c-dw-v6-1-08ca1e9ece07@bootlin.com