target/riscv-013: fix unused initialization

Scan-build reports:
	Unused code: Dead initialization
	riscv-013.c:2362 Value stored to 'control' during its
		initialization is never read

Remove the initialization of variable 'control'.

Change-Id: I548f8175530b9a2aa4c1788549d6467bf9824584
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7206
Reviewed-by: Tim Newsome <tim@sifive.com>
Reviewed-by: Jan Matyas <matyas@codasip.com>
Tested-by: jenkins

src/target/riscv/riscv-013.c

@@ -2359,9 +2359,7 @@ static int assert_reset(struct target *target)
 		/* TODO: Try to use hasel in dmcontrol */
 
 		/* Set haltreq for each hart. */
-		uint32_t control = control_base;
-
-		control = set_hartsel(control_base, target->coreid);
+		uint32_t control = set_hartsel(control_base, target->coreid);
 		control = set_field(control, DM_DMCONTROL_HALTREQ,
 				target->reset_halt ? 1 : 0);
 		dmi_write(target, DM_DMCONTROL, control);