Bug#904178: ffmpeg: fix mips r6 build

[YunQiang Su]

Package: src:ffmpeg
Version: 4.0.1-2

We are working on MIPS r6 ports.

Please change the lines about mips options in debian/rules to the below.
# Disable some optimizations on mips*, because they are not always
available on these architectures
ifneq (,$(filter mips%r6 mips%r6el, $(DEB_HOST_ARCH)))
        MIPS_NO_R6_OPTION = --disable-mips32r2 \
                --disable-mips64r2 \
                --disable-mips32r5
else
        MIPS_NO_R6_OPTION = --disable-mips32r6 \
                --disable-mips64r6
endif

ifneq (,$(filter mips%, $(DEB_HOST_ARCH)))
        CONFIG += --disable-mipsdsp \
                --disable-mipsdspr2 \
                --disable-loongson2 \
                --disable-loongson3 \
                --disable-mmi \
                --disable-mips32r5 \
                $(MIPS_NO_R6_OPTION) \
                --disable-msa
endif

-- 
YunQiang Su