tools/Makefile: Remove pci target

tools/Makefile: Remove pci target

e19bde2269ca ("selftests: Move PCI Endpoint tests from tools/pci to
Kselftests") moves tools/pci/ to tools/testing/selftests/pci_endpoint,
which causes build failure when running "make pci" under tools:

  linux/tools$ make pci
    DESCEND pci
  make[1]: *** No targets specified and no makefile found.  Stop.
  make: *** [Makefile:73: pci] Error 2

Update the top level tools/Makefile to remove reference to building,
installing and cleaning pci components.

Link: https://lore.kernel.org/r/20250217115159.537920-1-liujianfeng1994@gmail.com
Fixes: e19bde2269ca ("selftests: Move PCI Endpoint tests from tools/pci to Kselftests")
Signed-off-by: Jianfeng Liu <liujianfeng1994@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>