i2c: brcmstb: Add support for atomic transfers

i2c: brcmstb: Add support for atomic transfers

Add support for atomic transfers using polling mode with interrupts
intentionally disabled to get rid of the warning introduced by commit
63b96983a5dd ("i2c: core: introduce callbacks for atomic transfers")
during system reboot and power-off.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>