staging: ralink-gdma: Remove print statement on failure of devm_kzalloc

Remove print statement after failure of devm_kzalloc. Issue found with
Coccinelle.

Signed-off-by: Nishka Dasgupta <nishka.dasgupta@yahoo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>