jtag_vpi: fix signed/unsigned comparison jtag_vpi_stableclocks

Change-Id: Id2b00fbc8ba627f4465c109fbde6e010faaff9d2
Signed-off-by: Parshintsev Anatoly <anatoly.parshintsev@syntacore.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8462
Reviewed-by: Jan Matyas <jan.matyas@codasip.com>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>

src/jtag/drivers/jtag_vpi.c

@@ -461,7 +461,7 @@ static int jtag_vpi_stableclocks(unsigned int num_cycles)
 	unsigned int cycles_remain = num_cycles;
 	int nb_bits;
 	int retval;
-	const int CYCLES_ONE_BATCH = sizeof(tms_bits) * 8;
+	const unsigned int CYCLES_ONE_BATCH = sizeof(tms_bits) * 8;
 
 	/* use TMS=1 in TAP RESET state, TMS=0 in all other stable states */
 	memset(&tms_bits, (tap_get_state() == TAP_RESET) ? 0xff : 0x00, sizeof(tms_bits));