MIPS: Export {copy, clear}_page functions alongside their definitions

MIPS: Export {copy, clear}_page functions alongside their definitions

Now that EXPORT_SYMBOL can be used from assembly source, move the
EXPORT_SYMBOL invocations for the copy_page & clear_page functions to be
alongside their definitions.

With this change there are no longer any symbols exported from
mips_ksyms.c so remove the file.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14515/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>