arch/blackfin: Add kmalloc NULL tests

Check that the result of kmalloc is not NULL before passing it to other
functions.

In the first two cases, the new code returns -ENOMEM, which seems
compatible with what is done for similar functions for other architectures.

In the last two cases, the new code fails silently, ie just returns,
because the function has void return type.

The semantic match that finds this problem is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
expression *x;
identifier f;
constant char *C;
@@

x = \(kmalloc\|kcalloc\|kzalloc\)(...);
... when != x == NULL
    when != x != NULL
    when != (x || ...)
(
kfree(x)
|
f(...,C,...,x,...)
|
*f(...,x,...)
|
*x->f
)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>