usb: gadget: bdc: fix memory leak

If dma_pool_alloc() fails we are jumping to fail and releasing all the
bd_tables which have been added to the chain but we missed freeing this
bd_table which was just allocated and still not added to the chain of
bd_table.

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>