mISDN: Fix indenting in dsp_cmx.c

We used a script to indent this code back in 2012, but I guess it got
confused by the ifdefs and added some extra tabs.  This patch removes
them.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>