mips/mm/tlbex: remove new instance of __cpuinit that crept back in

We removed __cpuinit support (leaving no-op stubs) quite some time ago.
However a new instance was added in commit c5b36783
("MIPS: Add support for XPA.")

Since we want to clobber the stubs soon, get this removed now.

Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>