dmaengine: idxd: remove set but not used variable 'group'

dmaengine: idxd: remove set but not used variable 'group'

drivers/dma/idxd/sysfs.c: In function engine_group_id_store:
drivers/dma/idxd/sysfs.c:419:29: warning: variable group set but not used [-Wunused-but-set-variable]

It is not used, so remove it.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20200211135335.55924-1-yuehaibing@huawei.com
Signed-Off-By: Vinod Koul <vkoul@kernel.org>