* sysdeps/mips/sys/asm.h (PTR_ADDU): Use addu on mips32r6/mips64r6.
(PTR_ADDIU): Use addiu for mips32r6/mips64r6.
(PTR_SUBU): Use subu for mips32r6/mips64r6.
(PTR_SUBIU): Use subu for mips32r6/mips64r6 (subiu does not exist).
* sysdeps/mips/machine-gmon.h (PTR_ADDU_STRING) Use addu for
mips32r6/mips64r6.
(PTR_SUBU_STRING) Use subu for mips32r6/mips64r6.