e2fsck: Fix max size calculation for extent files

e2fsck: Fix max size calculation for extent files

A misunderstanding C's precedence rules and the meaning of
s_log_block_size meant that we were capping the maximum size of
extent-based files at 8GB instead of the 64TB that it should be for
filesystems with 4k block sizes.

Addresses-Kernel-Bugzilla: #11341

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