Staging: unisys: visorutil: Clean up sparse warnings in visorutil code

Clean up code to get rid of sparse warnings.

Also fixed variable length arrays declared on the stack by removing
visor_hexDumpToBuffer() and using hex_dump_to_buffer() instead.

Signed-off-by: Ken Cox <jkc@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>