xilinx: Only enable dist boot pxe when DHCP is enabled

Otherwise, we see this:
In file included from include/configs/zynq-common.h:183:0,
                 from include/config.h:5,
                 from include/common.h:21,
                 from env/common.c:11:
include/config_distro_bootcmd.h:319:2: error: expected ?}? before ?BOOT_TARGET_DEVICES_references_PXE_without_CONFIG_CMD_DHCP_or_PXE?
  BOOT_TARGET_DEVICES_references_PXE_without_CONFIG_CMD_DHCP_or_PXE
  ^
include/config_distro_bootcmd.h:319:2: note: in definition of macro ?BOOTENV_DEV_NAME_PXE?

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

include/configs/socfpga_common.h

@@ -292,7 +292,7 @@ unsigned int cm_get_qspi_controller_clk_hz(void);
 #define BOOT_TARGET_DEVICES_DHCP(func)
 #endif
 
-#ifdef CONFIG_CMD_PXE
+#if defined(CONFIG_CMD_PXE) && defined(CONFIG_CMD_DHCP)
 #define BOOT_TARGET_DEVICES_PXE(func) func(PXE, pxe, na)
 #else
 #define BOOT_TARGET_DEVICES_PXE(func)

include/configs/xilinx_zynqmp.h

@@ -172,7 +172,7 @@
 # define BOOT_TARGET_DEVICES_USB(func)
 #endif
 
-#if defined(CONFIG_CMD_PXE)
+#if defined(CONFIG_CMD_PXE) && defined(CONFIG_CMD_DHCP)
 # define BOOT_TARGET_DEVICES_PXE(func)	func(PXE, pxe, na)
 #else
 # define BOOT_TARGET_DEVICES_PXE(func)

include/configs/zynq-common.h

@@ -162,7 +162,7 @@
 #define BOOT_TARGET_DEVICES_USB(func)
 #endif
 
-#if defined(CONFIG_CMD_PXE)
+#if defined(CONFIG_CMD_PXE) && defined(CONFIG_CMD_DHCP)
 #define BOOT_TARGET_DEVICES_PXE(func) func(PXE, pxe, na)
 #else
 #define BOOT_TARGET_DEVICES_PXE(func)