drivers: dma: warn if ioremap fails

dma-removed alloc hook tries to ioremap a carve-out in order
to memset it to 0s. Warn the user if it fails due to low
vmalloc space.

CRs-fixed: 652009
Change-Id: If8d1a220c8e604222a44c5bf5201fc2d03e370b8
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>
arm: dma-removed: Add option to skip buffer zeroing

The DMA framework currently zeros all buffers because it (righfully so)
assumes that drivers will soon need to pass the memory to a device.
Some devices/use case may not require zeroed memory and there can
be an increase in performance if we skip the zeroing. Use the
DMA_ATTR_SKIP_ZEROING attr to allow skipping of DMA zeroing.

Change-Id: Ie7a8ae547834c29a6a4f327095e099c53526f3f7
Signed-off-by: Taniya Das <tdas@codeaurora.org>