Commit 0046be10e0c502705fc74d91408eba13a73bc201 ("mips: delete
non-required instances of include <linux/init.h>") inadvertently
removed an include that was actually correct.  Restore it.

Note that it gets init.h implicitly anyway, so this is largely a
cosmetic fixup; no build regressions were caused by this.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6416/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>