ocfs2_dlmfs: Fix math error when reading LVB.
ocfs2_dlmfs: Fix math error when reading LVB.

When asked for a partial read of the LVB in a dlmfs file, we can
accidentally calculate a negative count.

Reported-by: Dan Carpenter <72501f147b2753e6660fdce744d9ac3084854f5e@gmail.com>
Cc: <4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@kernel.org>
Signed-off-by: Joel Becker <823d0e2e55da83c1616b20ae9a15f9456fa076e5@oracle.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs