Staging: echo: fix kmalloc()/kfree() uses

This patch removes the malloc()/free() macro wrappers and converts
call-sites to use kcalloc() and kzalloc() where appropriate. I also
fixed up out-of-memory error handling in couple of places where it was
broken.

Cc: David Rowe <david@rowetel.com>
Cc: Steve Underwood <steveu@coppice.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>