resize2fs: enforce the 16TB limit on 32-bit file systems correctly

resize2fs: enforce the 16TB limit on 32-bit file systems correctly

The 16TB limit must be enforced regardless of whether the new size is
specified on the command line or implied by the size of the device,
but only if the file system does not support 64-bit block sizes, or
the kernel does not advertise support of meta_bg resizing.

Previously we were unconditionally enforcing it when it was implied by
the device size, but not if the new size was specified on the command
line.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>