dmaengine: idxd: Fix clobbering of SWERR overflow bit on writeback

dmaengine: idxd: Fix clobbering of SWERR overflow bit on writeback

[ Upstream commit ea941ac294d75d0ace50797aebf0056f6f8f7a7f ]

Current code blindly writes over the SWERR and the OVERFLOW bits. Write
back the bits actually read instead so the driver avoids clobbering the
OVERFLOW bit that comes after the register is read.

Fixes: bfe1d56091c1 ("dmaengine: idxd: Init and probe for Intel data accelerators")
Reported-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/161352082229.3511254.1002151220537623503.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>