dmaengine: Remove redundant initialization of variable err

The variable err is being initialized with a value that is never read, it
is being updated later on. The assignment is redundant and can be removed
and move the declaration into the local scope.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20211015123447.27560-1-colin.king@canonical.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>