[pxe] Remove obsolete references to pxeparent_dhcp

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/prefix/kkkpxeprefix.S

 
 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL )
 
-/* Since we have the whole stack, we can use cached DHCP information */
-REQUIRE_OBJECT ( pxeparent_dhcp )
-
 /* Provide the PXENV_FILE_EXIT_HOOK API call */
 REQUIRE_OBJECT ( pxe_exit_hook )
 

src/arch/i386/prefix/kkpxeprefix.S

 
 FILE_LICENCE ( GPL2_OR_LATER )
 
-/* Since we have the whole stack, we can use cached DHCP information */
-REQUEST_OBJECT ( pxeparent_dhcp )
-
 #define PXELOADER_KEEP_UNDI
 #define PXELOADER_KEEP_PXE
 #define _pxe_start _kkpxe_start