staging: mt7621-dma: Remove unnecessary line continuations

checkpatch message:
"WARNING:LINE_CONTINUATIONS: Avoid unnecessary line continuations"

Signed-off-by: Frank A. Cancio Bello <frank@generalsoftwareinc.com>
Link: https://lore.kernel.org/r/20191028051237.3row7xnbr6pgn4bp@linux-kernel-dev


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>