dmaengine: vdma: Fix race condition in Non-SG mode

When VDMA is configured in  Non-sg mode
Users can queue descriptors greater than h/w configured frames.

Current driver allows the user to queue descriptors upto h/w configured.
Which is wrong for non-sg mode configuration.

This patch fixes this issue.

Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>