spi_qsd: support to transfer 64K chunks in DM mode

Support to transfer 64K bytes in a single SPI
transfer in DMA mode on targets which support
16 bits in QUP_MX_OUTPUT_CNT register. Earlier
if the application sends more than 4K data it is
split up in to 4K chunks,  irrespective of the size
of the QUP_MX_OUTPUT_CNT register.

CRs-Fixed: 383120
Change-Id: Ibbe73df2bb4fb2804ff6ebfc62adac9d0d53e9cd
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>