i2c: add a message flag for DMA safe buffers

i2c: add a message flag for DMA safe buffers

BugLink: https://bugs.launchpad.net/bugs/1787775
From: Wolfram Sang <wsa+renesas@sang-engineering.com>

I2C has no requirement that the buffer of a message needs to be DMA
safe. In case it is, it can now be flagged, so drivers wishing to
do DMA can use the buffer directly.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
(cherry picked from commit 521a72e1f2e8141d78e7699eaacda24e308ed428)
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Acked-by: Khalid Elmously <khalid.elmously@canonical.com>
Acked-by: Kleber Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>