PCI: Sort controller Kconfig entries by vendor

Sort Kconfig entries by vendor so they appear in alphabetical order in
menuconfig.

Link: https://lore.kernel.org/r/20230418174336.145585-6-helgaas@kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Author: bjorn-helgaas