MIPS: Remove __invalidate_kernel_vmap_range

The __invalidate_kernel_vmap_range function pointer global variable
isn't used anywhere. Remove it.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: trivial@kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17174/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>