Remove use of LFS64 interfaces

Remove use of LFS64 interfaces

LFS64 interfaces are non-standard and are being removed in the upcoming musl
1.2.5. Setting _FILE_OFFSET_BITS=64 (which is currently being done) makes all
interfaces on glibc 64-bit by default, so using the LFS64 interfaces is
redundant. This commit replaces all occurences of off64_t with off_t,
stat64 with stat, and fstat64 with fstat.

Link: https://bugs.gentoo.org/907039
Cc: Felix Janda <felix.janda@posteo.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Violet Purcell <vimproved@inventati.org>
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>