PCI: Apply CONFIG_PCI_DEBUG to entire drivers/pci hierarchy

CONFIG_PCI_DEBUG=y adds -DDEBUG to CFLAGS, which enables things like
pr_debug() and dev_dbg() (and hence pci_dbg()).  Previously we added
-DDEBUG for files in drivers/pci/, but not files in subdirectories of
drivers/pci/.

Add -DDEBUG to CFLAGS for all files below drivers/pci/ so CONFIG_PCI_DEBUG
applies to the entire hierarchy.

[bhelgaas: commit log]
Link: https://lore.kernel.org/r/1612438215-33105-1-git-send-email-yangyicong@hisilicon.com
Signed-off-by: Junhao He <hejunhao2@hisilicon.com>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Krzysztof Wilczyński <kw@linux.com>

drivers/pci/Makefile

@@ -36,4 +36,4 @@ obj-$(CONFIG_PCI_ENDPOINT)	+= endpoint/
 obj-y				+= controller/
 obj-y				+= switch/
 
-ccflags-$(CONFIG_PCI_DEBUG) := -DDEBUG
+subdir-ccflags-$(CONFIG_PCI_DEBUG) := -DDEBUG