dev/mfi: Make a seemingly bogus conditional unconditional

Summary:
r358689 attempted to fix a clang warning/error by inferring the intent
of the condition "(cdb[0] != 0x28 || cdb[0] != 0x2A)". Unfortunately, it looks
like this broke things. Instead, fix this by making this path unconditional,
effectively reverting to the previous state.

PR: kern/251483
Reviewed By: ambrisko
MFC after: 2 days
Differential Revision: https://reviews.freebsd.org/D27515