staging:nvec: Introduce the use of the managed version of kzalloc

This patch moves shared private data kzalloc to managed devm_kzalloc.
There are no kfree statements associated with this data, so using devm
adds the possibility of the data being freed, if the proble function
fails (if that is possible) or if the remove function succeeds.

Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>