[MIPS] Add __cmpdi2

Certain 32-bit kernel configurations seem to be able to cause references,
this was observed with gcc 4.1.2.

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

arch/mips/lib/Makefile

@@ -28,4 +28,4 @@ obj-$(CONFIG_CPU_TX49XX)	+= dump_tlb.o
 obj-$(CONFIG_CPU_VR41XX)	+= dump_tlb.o
 
 # libgcc-style stuff needed in the kernel
-obj-y += ashldi3.o ashrdi3.o lshrdi3.o ucmpdi2.o
+obj-y += ashldi3.o ashrdi3.o cmpdi2.o lshrdi3.o ucmpdi2.o