samples: mpssd: fix the build errors when enable DEBUG in mpssd.c

samples: mpssd: fix the build errors when enable DEBUG in mpssd.c

If enable DEBUG, will meet the following errors when build mpssd, so fix
them here. Only one error is listed here, other errors are similar.

mpssd.c: In function ‘virtio_net’:
mpssd.c:615:21: error: incompatible type for argument 2 of ‘disp_iovec’
     disp_iovec(mic, copy, __func__, __LINE__);
                     ^~~~
mpssd.c:361:1: note: expected ‘struct mic_copy_desc *’ but argument is of type ‘struct mic_copy_desc’
 disp_iovec(struct mic_info *mic, struct mic_copy_desc *copy,
 ^~~~~~~~~~

Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20200925071831.8025-2-sherry.sun@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>