i2c: testunit: don't erase registers after STOP

STOP fallsthrough to WRITE_REQUESTED but this became problematic when
clearing the testunit registers was added to the latter. Actually, there
is no reason to clear the testunit state after STOP. Doing it when a new
WRITE_REQUESTED arrives is enough. So, no need to fallthrough, at all.

Fixes: b39ab96 ("i2c: testunit: add support for block process calls")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>

Author: Wolfram Sang

drivers/i2c/i2c-slave-testunit.c

@@ -118,7 +118,7 @@ static int i2c_slave_testunit_slave_cb(struct i2c_client *client,
 			queue_delayed_work(system_long_wq, &tu->worker,
 					   msecs_to_jiffies(10 * tu->regs[TU_REG_DELAY]));
 		}
-		fallthrough;
+		break;
 
 	case I2C_SLAVE_WRITE_REQUESTED:
 		memset(tu->regs, 0, TU_NUM_REGS);