msm: buspm: Remove allocate_contiguous_ebi calls

allocate_contiguous_ebi is being deprecated in favor of the standard
dma_alloc_coherent APIs. Move accordingly.

Change-Id: I3746e5ac047b1a6ee570aaf96ffbe305e3b6a49f
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>