core/kmod: use kmalloc instead of kzalloc

There's no need to zero out the kpatch funcs array.  The addr fields are
initialized by the patch module, the mod field is intialized by the core
module, and the node struct doesn't need to be initialized because its
fields are overwritten by hash_add.
Merge pull request #68 from jpoimboe/core-no-kzalloc

core/kmod: use kmalloc instead of kzalloc