20.11-rc SPDX compliance report

Current output of check-spdx-tag.sh

Files without SPDX License
--------------------------
doc/guides/custom.css
doc/guides/linux_gsg/nic_perf_intel_platform.rst
drivers/net/iavf/rte_pmd_iavf.h
examples/multi_process/Makefile
examples/multi_process/client_server_mp/Makefile
lib/librte_eal/windows/eal_hugepages.c

Files with redundant license text
---------------------------------
app/test/test_timer_racecond.c

total: 6 errors, 1 warnings

'rte_pmd_iavf.h' has SPDX license but there is typo in it, I will send a quick patch for it.