libext2fs: fix off-by-one bug in punch_extent_blocks

libext2fs: fix off-by-one bug in punch_extent_blocks

punch_extent_blocks tries to validate its input parameters to make sure
that the physical range of blocks being punched do not go past the end
of the filesystem.  Unfortunately, there's an off-by-one bug in the
valiation, because start==0 count==10 is a perfectly valid range on a
10-block filesystem.

Cc: linux-ext4@vger.kernel.org # v1.46.6
Fixes: 6772d4969e9c90 ("libext2fs: check for invalid blocks in ext2fs_punch_blocks()")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/175182662987.1984706.5292286424808159532.stgit@frogsfrogsfrogs
Signed-off-by: Theodore Ts'o <tytso@mit.edu>