vt: keyboard.c: make console an unsigned int

vt: keyboard.c: make console an unsigned int

The console variable is used everywhere in some fun pointer path and
array indexes and for some reason isn't always declared as unsigned.
This plays havoc with some static analysis tools so mark the variable as
unsigned so we "know" we can not wrap the arrays backwards here.

Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reported-by: Jordy Zomer <jordy@pwning.systems>
Link: https://lore.kernel.org/r/20210726134322.2274919-2-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>