host-libusb: Remove unused variable

Variable unconnected used in usb_host_auto_check function is only incremented
but never read as line where it is read was disabled since introducing the code.
This causes 'Unused but set variable' warning on Clang 15.0.1 compiler.

Removing the variable and disabled code to prevent the warning.

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <00df0db69ff9167d38bac81f6d03281955bd861a.1668009030.git.mrezanin@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>