UBUNTU: SAUCE: fs: Move SB_I_NOSUID to the top of s_iflags

UBUNTU: SAUCE: fs: Move SB_I_NOSUID to the top of s_iflags

BugLink: https://bugs.launchpad.net/bugs/1851677
SB_I_NOSUID was added by a sauce patch, and over time it has come
to occpy the same bit in s_iflags as SB_I_USERNS_VISIBLE without
being noticed. overlayfs will set SB_I_NOSUID when any lower
mount is nosuid. When this happens for a user namespace mount,
mount_too_revealing() will perform additional, unnecessary checks
which may block mounting when it should be allowed.

Move SB_I_NOSUID to prevent this conflict, and move it to the top
of s_iflags to make future conflicts less likely.

Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>