mips: i6400 core is not mips32r2, so disable mips32r2

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

configure

@@ -4163,6 +4163,7 @@ elif enabled mips; then
             add_asflags "-mfp64"
         ;;
         i6400)
+            disable mips32r2
             disable mipsdsp
             disable mipsdspr2
             check_cflags "-mtune=i6400 -mabi=64" &&