dmaengine: add Qualcomm BAM dma driver

Add the DMA engine driver for the QCOM Bus Access Manager (BAM) DMA controller
found in the MSM 8x74 platforms.

Each BAM DMA device is associated with a specific on-chip peripheral.  Each
channel provides a uni-directional data transfer engine that is capable of
transferring data between the peripheral and system memory (System mode), or
between two peripherals (BAM2BAM).

The initial release of this driver only supports slave transfers between
peripherals and system memory.

Signed-off-by: Andy Gross <agross@codeaurora.org>
Tested-by: Stanimir Varbanov <svarbanov@mm-sol.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>