tools/console: Use const whenever we point to literal strings

tools/console: Use const whenever we point to literal strings

Literal strings are not meant to be modified. So we should use const
char * rather than char * when we want to store a pointer to them.

Take the opportunity to remove the cast (char *) in console_init(). It
is unnecessary and will remove the const.

Signed-off-by: Julien Grall <jgrall@amazon.com>
Acked-by: Wei Liu <wl@xen.org>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>