PCI: tegra264: Fix RP off support

We cannot use enum definitions in '#if defined()' statements because the
'#if defined()' is a preprocessor macro that is evaluated prior to
compilation. Fix this by adding a test to conftest to detect if
CMD_PCIE_RP_CONTROLLER_OFF is defined.

Bug 5551652

Change-Id: I71826a58e428f1a335e8e0d895f25f3cea46a65e
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3467641
GVS: buildbot_gerritrpt <buildbot_gerritrpt@nvidia.com>
Reviewed-by: Prakhar Srivastava (SW-TEGRA) <prasrivastav@nvidia.com>

scripts/conftest/conftest.sh

@@ -6945,6 +6945,23 @@ compile_test() {
             compile_check_conftest "$CODE" "NV_CLK_HW_DETERMINE_RATE_NO_REPARENT_PRESENT" "" "functions"
         ;;
 
+        cmd_pcie_rp_controller_off_enum_present)
+            #
+            # Determine if the enum mrq_pcie_cmd defines the values
+            # CMD_PCIE_RP_CONTROLLER_OFF.
+            #
+            # This is only defined in NVIDIA kernels at the moment.
+            #
+            CODE="
+            #include <linux/types.h>
+            #include <soc/tegra/bpmp-abi.h>
+            int conftest_cmd_pcie_rp_controller_off_enum_present(void) {
+                return CMD_PCIE_RP_CONTROLLER_OFF;
+            }"
+
+            compile_check_conftest "$CODE" "NV_CMD_PCIE_RP_CONTROLLER_OFF_ENUM_PRESENT" "" "types"
+        ;;
+
         cyclecounter_struct_read_has_const_cyclecounter_arg)
             #
             # Determine if the 'cyclecounter' structure 'read' function pointer