Add necessary files (such as *.h) in module msa and remove unused msa files.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@882 6f19259b-4bc3-4df7-8a09-765794883524

EdkModulePkg/Universal/Network/PxeBc/Dxe/BC.msa

@@ -67,6 +67,8 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.-->
     <Filename>pxe_bc_mtftp.c</Filename>
     <Filename>pxe_bc_udp.c</Filename>
     <Filename>pxe_loadfile.c</Filename>
+    <Filename>hton.h</Filename>
+    <Filename>tftp.h</Filename>
     <Filename>dhcp.h</Filename>
     <Filename>bc.h</Filename>
     <Filename>ip.h</Filename>