libext2fs: don't overflow when punching indirect blocks with large blocks

libext2fs: don't overflow when punching indirect blocks with large blocks

On a FS with a rather large blockize (> 4K), the old block map
structure can construct a fat enough "tree" (or whatever we call that
lopsided thing) that (at least in theory) one could create mappings
for logical blocks higher than 32 bits.  In practice this doesn't
happen, but the 'max' and 'iter' variables that the punch helpers use
will overflow because the BLOCK_SIZE_BITS shifts are too large to fit
a 32-bit variable.  The current variable declarations also cause punch
to fail on TIND-mapped blocks even if the file is < 16T.  So enlarge
the fields to fit.

Yes, this is an obscure corner case, but it seems a little silly if we
can't punch a file's block 300,000,000 on a 64k-block filesystem.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>