dmaengine: qcom: bam_dma: wrapper functions for command descriptor

QCOM BAM also supports command descriptor which allows the SW to
create descriptors of type command which does not generate any
data transmissions but configures registers in the peripheral.
In command descriptor the 32bit address point to the start of
the command block which holds the command elements and the
16bit size define the size of the command block.

Each Command Element is structured by 4 words:
    Write command: address + cmd
                   register data
                   register mask
                   reserved

    Read command: address + cmd
                  read data result address,
                  reserved
                  reserved

This patch creates a new header file for BAM driver which contains the
structures and wrapper functions for command descriptor. This file will
be used by different QCOM peripheral drivers for forming the command
descriptor

Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>