when quit from ASRC driver with CTRL + C, driver close() would free
output buffer and close clock. However, it is possible that the buffer
is accessed by work task(work task is trigger by interrupt and it would
not be stopped by CTRL + C). So ASRC driver should promise that  its
pair resource(buffer, SDMA channel, and clock) would not be accessed
after it is released.

In this patch, add protect for pair resource.

Signed-off-by: Chen Liangjun <b36089@freescale.com>