As noted by c1f0601389db64d9, previous posix_fadvise consolidation
broke on mips o32. As stated in commit message, MIPS o32 only defines
__NR_fadvise64 and it is behaves like __NR_fadvise64_64.
This patches consolidates both ARM and mips o32 version by fixing
the ARM used option (__NR_fadvise64_64 withouth the alignment required
by abi) and added another option, __ASSUME_FADVISE64_AS_64_64,
which is used on mips o32.
When this option is used, posix_fadvise will use __NR_fadvise64_64
behavior (by defining or not __ASSUME_FADVISE64_64_6ARG). For
mips, if __NR_fadvise64_64 is not defined, __NR_fadvise will be used.
I also updated the posix_fadvise comments to explain better the
different kernel abi used in the supported architectures.
I checked with a mips o32 and verified that posix_fadvise.o is
indeed using 7 argument syscall with the expected argument position.
I also checked on i686-linux-gnu and arm-gnu-eabihf.
* sysdeps/unix/sysv/linux/arm/posix_fadvise.c: Remove file.
* sysdeps/unix/sysv/linux/mips/mips32/posix_fadvise.c: Likewise.
* sysdeps/unix/sysv/linux/mips/kernel-features.h
(__ASSUME_FADVISE64_AS_64_64): Define.
* sysdeps/unix/sysv/linux/posix_fadvise.c [__NR_fadvise64]: Add
!defined __ASSUME_FADVISE64_AS_64_64 to use syscall issue.
[!__NR_fadvise64 && __ASSUME_FADVISE64_64_6ARG]: Remove
__ALIGNMENT_ARG usage.
[!__NR_fadvise64 && !__ASSUME_FADVISE64_64_6ARG]: Define
__NR_fadvise64_64 if it is not defined.
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