msm: kgsl: Don't allow an offset when importing dma-buf buffers

The offset member is ignored when importing dma-buf buffers
but it is used to calculate the final GPU address. Explicitly
reject offsets for dma-buf buffers and as a double bonus fix
the offset alignment for those memory types that might still
use it.

Change-Id: Ic0dedbad898b7d6470337b00a176f41cc2456209
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>