include/linux/fs.h: fix userspace build

dpkg uses fiemap but didn't particularly need to include stdint.h so far.
Since 367a51a ("fs: Add FITRIM ioctl"), build of linux/fs.h failed in
dpkg with:

  In file included from ../../src/filesdb.c:27:0:
  /usr/include/linux/fs.h:37:2: error: expected specifier-qualifier-list before 'uint64_t'

Use exportable type __u64 to avoid the dependency on stdint.h.

b31d42a ("Fix compile brekage with !CONFIG_BLOCK") fixed only the
kernel build by including linux/types.h, but this also fixed "make
headers_check", so don't revert it.

Signed-off-by: Loïc Minier <[email protected]>
Tested-by: Arnd Bergmann <[email protected]>
Cc: Lukas Czerner <[email protected]>
Cc: Dmitry Monakhov <[email protected]>
Cc: Theodore Ts'o <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/fs.h

@@ -34,9 +34,9 @@
 #define SEEK_MAX	SEEK_END
 
 struct fstrim_range {
-	uint64_t start;
-	uint64_t len;
-	uint64_t minlen;
+	__u64 start;
+	__u64 len;
+	__u64 minlen;
 };
 
 /* And dynamically-tunable limits and defaults: */