MIPS: fix *-pkg builds for loongson2ef platform

Hello, stable maintainers.

I'd like to request the change made by cca2aac8acf470b01066f559acd7146fc4c32ae8 be applied to the 5.15 and 5.14 series so as to address the build failure. That patch doesn't apply to 5.14 as-is so I am attaching a backported version of the patch that does.