iio: scmi: fix spelling of SPDX tag

checkpatch looks for SPDX-License-Identifier.
Remove the extra spaces.

Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20210610214438.3161140-7-trix@redhat.com


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