arm64: xilinx: Guard distro boot variable generation

When distro boot is disabled there is no reason to generate variables for
it. Also do not update boot_targets variable because it would be unused.

It is useful for example when standard boot is enabled and distro boot
is disabled.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/570c51435da59831ec245cddceda078afa58a550.1693913398.git.michal.simek@amd.com
diff --git a/include/configs/xilinx_zynqmp.h b/include/configs/xilinx_zynqmp.h
index 51f0a42..c57ab14 100644
--- a/include/configs/xilinx_zynqmp.h
+++ b/include/configs/xilinx_zynqmp.h
@@ -63,6 +63,8 @@
 	"stdout=serial,vidconsole\0" \
 	"stderr=serial,vidconsole\0" \
 
+#if defined(CONFIG_DISTRO_DEFAULTS)
+
 #if defined(CONFIG_MMC_SDHCI_ZYNQ)
 # define BOOT_TARGET_DEVICES_MMC(func)	func(MMC, mmc, 0) func(MMC, mmc, 1)
 #else
@@ -174,6 +176,10 @@
 
 #include <config_distro_bootcmd.h>
 
+#else /* CONFIG_DISTRO_DEFAULTS */
+# define BOOTENV
+#endif /* CONFIG_DISTRO_DEFAULTS */
+
 /* Initial environment variables */
 #ifndef CFG_EXTRA_ENV_SETTINGS
 #define CFG_EXTRA_ENV_SETTINGS \