Fix typeo in LoadBinariesViaExhaustiveSearch when looking for kernel

As a last resort, with a Mach-O corefile, lldb will iterate through
all memory segments looking for a dyld binary (for a userland process
core dump) or an xnu kernel binary (kernel coredump).  We often
have metadata via LC_NOTEs so this final search mechanism is not
needed.  During the rewrite in https://reviews.llvm.org/D133680 I
did not handle the case of finding the xnu kernel by exhaustive
search correctly.

rdar://103813200