net: Get pxe config file from dhcp option 209

Allow dhcp server pass pxe config file full path by using option 209

Signed-off-by: Sean Edmond <seanedmond@microsoft.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index fd16c3a..df6d71c 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1840,6 +1840,10 @@
 	default 0x15 if ARM
 	default 0x0 if X86
 
+config BOOTP_PXE_DHCP_OPTION
+	bool "Request & store 'pxe_configfile' from BOOTP/DHCP server"
+	depends on BOOTP_PXE
+
 config BOOTP_VCI_STRING
 	string
 	depends on CMD_BOOTP