qaic: Return the number of queued elements for debugfs queued

Currently the debugfs queued entry returns the available slots in the
DMA bridge request queue. The intention of the entry is to return the
number of elements in the queue. This patch fixes it.

Change-Id: I4f3adcef587e565e1e7c83f06ff58e7b4c080785
Signed-off-by: Fan Wu <wufan@codeaurora.org>
Signed-off-by: Pratyush Anand <pratanan@codeaurora.org>