Hexagon (target/hexagon) fix bug in circular addressing

Versions V3 and earlier should treat the "K_const" and "length" values
as unsigned.

Modified circ_test_v3() in tests/tcg/hexagon/circ.c to reproduce the bug

Signed-off-by: Michael Lambert <mlambert@quicinc.com>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <20220210021556.9217-2-tsimpson@quicinc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>