This massive rename is result of Pavel Machek's review to remove the second
line from from next Kbuild fragment

  obj-$(CONFIG_CAN_CTUCANFD_PLATFORM) += ctucanfd_platform.o
  ctucanfd_platform-y += ctu_can_fd_platform.o

Change is done in C file names only for now, change in VHDL sources
and generated header files would represents more than 4k occurrences
changes, complete break of readable blame histories tests etc...
If ever done then it would require team support.

Header files generator
  scripts/pyXact_generator/HeaderAddrGeneratorWrapper.py
should be updated as well

-                            headerGen.prefix = "ctu_can_fd"
+                            headerGen.prefix = "ctucanfd"
                             headerGen.create_addrMap_package(self.headName)

but such change would result in massive driver files changes.

Rename is done in multiple steps to ensure 100%/complete files
without content touching rename and then update and remove
of support targets and symlinks which allows to keep original
file content for the first step. This way it should allow
to git tools to guess renames right and allows to audit changes,
do bisects and all other stuff over renames.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>