fstests: Replace all __[u]intNN_t types with standard [u]intNN_t

fstests: Replace all __[u]intNN_t types with standard [u]intNN_t

Integer types such as __uint32_t are non-standard and not supported
by some C libraries such as musl. This commit replaces them with
standard types such as uint32_t and includes stdint.h header where
necessary.

The following command was used to do the changing of types:
sed -r -i 's/__(u?int[0-9]{2}_t)/\1/g' src/*.c ltp/*.c

Signed-off-by: Rostislav Skudnov <rostislav@tuxera.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eryu Guan <eguan@redhat.com>