arm: tegra: add options for BOOTENV_EFI_SET_FDTFILE_FALLBACK for tegra186

Upstream linux DT naming doesn't align with the U-Boot DT, which may
not always be the case so this allows using BOOTENV_EFI_SET_FDTFILE_FALLBACK
where it might be appropriate for some boards.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/include/config_distro_bootcmd.h b/include/config_distro_bootcmd.h
index ff29ef5..82a3a36 100644
--- a/include/config_distro_bootcmd.h
+++ b/include/config_distro_bootcmd.h
@@ -118,8 +118,10 @@
 	  "setenv efi_fdtfile ${soc}-${board}${boardver}.dtb; "           \
 	"fi; "
 #else
+#ifndef BOOTENV_EFI_SET_FDTFILE_FALLBACK
 #define BOOTENV_EFI_SET_FDTFILE_FALLBACK
 #endif
+#endif
 
 
 #define BOOTENV_SHARED_EFI                                                \