iio: imu: fix spdx format

checkpatch reports
WARNING: Missing or malformed SPDX-License-Identifier tag in line 1
FILE: drivers/iio/imu/bno055/bno055_ser_trace.c:1:
+//SPDX-License-Identifier: GPL-2.0

Add a space

Fixes: 2eef5a9c ("iio: imu: add BNO055 serdev driver")
Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20230124194301.656518-1-trix@redhat.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>