[PATCH 2/5] license: Fix SPDX identifiers

[PATCH 2/5] license: Fix SPDX identifiers

Some files still carried GPL identifiers. These were identified and
updated. Thus, all files should carry the LGPL identifier now.

Files with incorrect identifiers were found with:
`grep -irnI --exclude-dir={build,.git,cpu_features} GPL . | grep -v LGPL`

Fixes #613

Signed-off-by: Johannes Demel <demel@uni-bremen.de>
Gbp-Pq: Name 0002-license-Fix-SPDX-identifiers.patch