configure: loongson disable mipsfpu and mipsdsp optimizations

The optimizations of mipsdsp are not supported by all loongson cpu.
The optimizations of mipsfpu and mipsdspr2 maybe supported by 3A2000/3A3000/3A4000 but not tested yet.
Loongson only support mmi (loongSIMD) optimizations now.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

configure

@@ -4380,6 +4380,9 @@ elif enabled mips; then
                 enable fast_cmov
                 enable fast_unaligned
                 disable aligned_stack
+                disable mipsfpu
+                disable mipsdsp
+                disable mipsdspr2
                 case $cpu in
                     loongson3*)
                         cpuflags="-march=loongson3a -mhard-float -fno-expensive-optimizations"