mips_attributes was introduced to work around clang problems with
-msoft-float. Those problems are now fixed and moreover .gnu_attributes
itself is unportable and creates problem with clang.
Revert "mips: Fix soft-float handling."
This partially reverts commit 6a4ecd276e.
Add -msoft-float alongside clang arguments to specify ABI.
Specify ABI in asm files explicitly.
This trigers asm warning due to gcc failing to propagate -msoft-float
but it's tolerable.
