ANDROID: dm-default-key: avoid truncating the logical block size

Upstream commit ad6bf88a ("block: fix an integer overflow in logical
block size") changed queue_limits::logical_block_size from 'unsigned
short' to 'unsigned int', and this commit has been backported to the LTS
branches.  Update the computation in default_key_io_hints() to match.

This mirrors upstream commit 64611a15 ("dm crypt: avoid truncating
the logical block size") which fixed the same bug in dm-crypt.

Fixes: cb39ec0c ("ANDROID: dm: add dm-default-key target for metadata encryption")
Change-Id: I98dd65afdb120073203af3b201d0831edd6e245c
Signed-off-by: Eric Biggers <ebiggers@google.com>