dmaengine: qcom_hidma: introduce memset support

HIDMA HW supports memset operation in addition to memcpy.
Since the memset API is present on the kernel now, bring the
memset feature into life.

The descriptor format is the same for both memcpy and memset.
Type of the descriptor is 4 when memset is requested.
The lowest 8 bits of the source DMA argument is used as a
fill pattern.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>