staging: et131x: Remove alignment offset padding on DMA buffer allocation/free

This padding was used to align buffers to a 4k boundary when returned
from dma_alloc_coherent(). As the buffers are already 4k aligned, and
the alignment no longer performed, the padding is not needed.

Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>