dmaengine: coh901318: Remove unused variable

Commit 627469e4 ("dmaengine: coh901318: Fix a double-lock bug") left
flags variable unused, so remove it to fix the warning.

drivers/dma/coh901318.c: In function 'coh901318_config':
drivers/dma/coh901318.c:1805:16: warning: unused variable 'flags' [-Wunused-variable]
  unsigned long flags;
                ^~~~~

Fixes: 627469e4

 ("dmaengine: coh901318: Fix a double-lock bug")
Reported-By: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Vinod Koul <vkoul@kernel.org>