MIPS: Use generic asm/export.h

Include export.h in the list of generic headers used by the MIPS
architecture for use by later patches.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14506/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/Kbuild

@@ -5,6 +5,7 @@ generic-y += cputime.h
 generic-y += current.h
 generic-y += dma-contiguous.h
 generic-y += emergency-restart.h
+generic-y += export.h
 generic-y += irq_work.h
 generic-y += local64.h
 generic-y += mcs_spinlock.h