i2c: xlp9xx: Check for Bus state before every transfer

i2c: xlp9xx: Check for Bus state before every transfer

BugLink: https://bugs.launchpad.net/bugs/1762812
I2C bus enters the STOP condition after the DATA_DONE interrupt is raised.
Essentially the driver should be checking the bus state before sending
any transaction. In case a transaction is initiated while the
bus is busy, the prior transaction's stop condition is not achieved.
Add the check to make sure the bus is not busy before every transaction.

Signed-off-by: George Cherian <george.cherian@cavium.com>
Reviewed-by: Jan Glauber <jglauber@cavium.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
(cherry picked from commit d3898a78521cd383d287b3ed5683f914c48c3be9)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>