PCI: Add PCIE_MSG_CODE_PME_TURN_OFF message macro

Add PCIE_MSG_CODE_PME_TURN_OFF macros to enable a PCIe host driver to send
PME_Turn_Off messages.

Link: https://lore.kernel.org/linux-pci/20240418-pme_msg-v8-4-a54265c39742@nxp.comSigned-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

drivers/pci/pci.h

@@ -30,6 +30,9 @@
 #define PCIE_MSG_TYPE_R_LOCAL	4
 #define PCIE_MSG_TYPE_R_GATHER	5
 
+/* Power Management Messages; PCIe r6.0, sec 2.2.8.2 */
+#define PCIE_MSG_CODE_PME_TURN_OFF	0x19
+
 /* INTx Mechanism Messages; PCIe r6.0, sec 2.2.8.1 */
 #define PCIE_MSG_CODE_ASSERT_INTA	0x20
 #define PCIE_MSG_CODE_ASSERT_INTB	0x21