crypto: msm: qce50: DMA-API buffers limitations

Not all memory are DMA'able. See DMA-API-HOWTO.txt. The dummy hash
request input buffer is changed to be acquired from coherent memory
to kzalloc().

Change-Id: If6961217df08bcf0506eedacb07874dfafd7c1ca
CRs-Fixed: 1064055
Acked-by: Che-Min Hsieh <cheminh@qti.qualcomm.com>
Signed-off-by: Sivanesan Rajapupathi <srajap@codeaurora.org>