Run 32-bit compat ldconfig on mips64.

mips64 supports COMPAT_FREEBSD32 (for o32 binaries), so run the 32-bit
compat ldconfig on it as well.

Reported by:	brooks
Reviewed by:	brooks, kib
Approved by:	re (gjb)
Differential Revision:	https://reviews.freebsd.org/D17342

sbin/init/rc.d/ldconfig

@@ -41,7 +41,7 @@ ldconfig_start()
 		${ldconfig} -elf ${_ins} ${_LDC}
 
 		case `sysctl -n hw.machine_arch` in
-		amd64|powerpc64)
+		amd64|mips64|powerpc64)
 			for i in ${ldconfig_local32_dirs}; do
 				if [ -d "${i}" ]; then
 					_files=`find ${i} -type f`