sunxi: Fix build when CONFIG_CMD_PXE or CONFIG_CMD_DHCP are disabled

Fixes a compilation failure with disabled PXE or DHCP command when using
sunxi platform.
Signed-off-by: NOndřej Jirman <megous@megous.com>
Reviewed-by: NJagan Teki <jagan@amarulasolutions.com>

include/configs/sunxi-common.h

@@ -393,6 +393,18 @@ extern int soft_i2c_gpio_scl;
 #define BOOT_TARGET_DEVICES_USB(func)
 #endif
 
+#ifdef CONFIG_CMD_PXE
+#define BOOT_TARGET_DEVICES_PXE(func) func(PXE, pxe, na)
+#else
+#define BOOT_TARGET_DEVICES_PXE(func)
+#endif
+
+#ifdef CONFIG_CMD_DHCP
+#define BOOT_TARGET_DEVICES_DHCP(func) func(DHCP, dhcp, na)
+#else
+#define BOOT_TARGET_DEVICES_DHCP(func)
+#endif
+
 /* FEL boot support, auto-execute boot.scr if a script address was provided */
 #define BOOTENV_DEV_FEL(devtypeu, devtypel, instance) \
 	"bootcmd_fel=" \
@@ -408,8 +420,8 @@ extern int soft_i2c_gpio_scl;
 	BOOT_TARGET_DEVICES_MMC(func) \
 	BOOT_TARGET_DEVICES_SCSI(func) \
 	BOOT_TARGET_DEVICES_USB(func) \
-	func(PXE, pxe, na) \
-	func(DHCP, dhcp, na)
+	BOOT_TARGET_DEVICES_PXE(func) \
+	BOOT_TARGET_DEVICES_DHCP(func)
 
 #ifdef CONFIG_OLD_SUNXI_KERNEL_COMPAT
 #define BOOTCMD_SUNXI_COMPAT \