mips/kprobes: Export kprobe_fault_handler()

Generic kprobe_page_fault() calls into kprobe_fault_handler() which must be
available with and without CONFIG_KPROBES. There is one stub implementation
for !CONFIG_KPROBES. For CONFIG_KPROBES all subscribing archs must provide
a kprobe_fault_handler() definition. Currently mips has an implementation
which is defined as 'static inline'. Make it available for generic kprobes
to comply with the above new requirement.

Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-mm@kvack.org

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Fixes: 773734b44557 ("mm, kprobes: generalize and rename notify_page_fault() as kprobe_page_fault()")
Cc: linux-kernel@vger.kernel.org