target: use boolean values for 'valid' and 'dirty' flags

Convert to boolean the remaining numeric assignment and comparison

Change-Id: Idc25221d93e85236185aab9ee36f0a379939c89c
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/7961
Reviewed-by: zapb <dev@zapb.de>
Tested-by: jenkins

src/target/etm.c

@@ -552,8 +552,8 @@ static int etm_set_reg(struct reg *reg, uint32_t value)
 	}
 
 	buf_set_u32(reg->value, 0, reg->size, value);
-	reg->valid = 1;
-	reg->dirty = 0;
+	reg->valid = true;
+	reg->dirty = false;
 
 	return ERROR_OK;
 }