Add a Coccinelle file to use the ERR_CAST function

Before the release 2.6.25, one had to use ERR_PTR(PTR_ERR(...))  to
convert the pointer type of an error. Since then, the function
ERR_CAST has been available for that purpose.
Signed-off-by: NNicolas Palix <npalix@diku.dk>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NMichal Marek <mmarek@suse.cz>