spi: spi_qsd: Add multi-ee support.

Add support for the same spi controller to be programmed
by the CPU and other execution environments rather than the
controller hw being owned by only one ee.

Change-Id: Id6560b9cb09ddf59045fdf48c713d14c5c013145
Signed-off-by: Dan Sneddon <dsneddon@codeaurora.org>