staging: et131x: Remove unnecessary DMA address alignment code

"The cpu return address and the DMA bus master address are both
guaranteed to be aligned to the smallest PAGE_SIZE order which
is greater than or equal to the requested size."

There are several places in the et131x.c code where these addresses are
aligned to a 4k boundary after a call to dma_alloc_coherent(),
needlessly.

Remove these alignment offset calculations, and the
et131x_align_allocated_memory() call which is only used for 4k
alignments.

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