MIPS: Export _mcount alongside its definition

Now that EXPORT_SYMBOL can be used from assembly source, move the
EXPORT_SYMBOL invocation for _mcount to be alongside its definition.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14525/


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