Don't error on block size mismatches.

liblp treats the term "block size" ambiguously when it compares the logical
hardware block size with the file system block size (which for all
intents and purposes must be 4K). This warning is thus spurious on
devices with say a 512 logical block size. However, liblp's block size
should at least be a multiple of this, so change the check accordingly.

Bug: 123317012
Test: liblp_test gtest
Change-Id: I0f41f6bae60a512ab8d313e487c28606daa661a6