[romprefix] Remove .xrom prefix

The .xrom prefix provides an experimental mechanism for loading ROM
images greater than 64kB in size by mapping the expansion ROM BAR in
at a hopefully-unused address.  This is unreliable, and potentially
dangerous.  In particular, there is no guarantee that any PCI bridges
between the CPU and the device will respond to accesses for the
"unused" memory region that is chosen, and it is possible that the
process of scanning for the "unused" memory region may end up issuing
reads to other PCI devices.  If this ends up trampling on a register
with read side-effects belonging to an unrelated PCI device, this may
cause undefined behaviour.

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

src/Makefile.housekeeping

@@ -867,8 +867,6 @@ endif # defined(BIN)
 FINALISE_rom	= $(MAKEROM) $(MAKEROM_FLAGS) $(TGT_MAKEROM_FLAGS) \
 		  -i$(IDENT) -s 0 $@
 FINALISE_hrom	= $(FINALISE_rom)
-FINALISE_xrom	= $(MAKEROM) $(MAKEROM_FLAGS) $(TGT_MAKEROM_FLAGS) \
-		  -i$(IDENT) -n -s 0 $@
 
 # Some ROMs require specific flags to be passed to makerom.pl
 #

src/arch/i386/Makefile.pcbios

@@ -12,7 +12,6 @@ LDFLAGS		+= -N --no-check-sections
 #
 MEDIA		+= rom
 MEDIA		+= hrom
-MEDIA		+= xrom
 MEDIA		+= pxe
 MEDIA		+= kpxe
 MEDIA		+= kkpxe
@@ -26,7 +25,6 @@ MEDIA		+= raw
 #
 PAD_rom		= $(PADIMG) --blksize=512 --byte=0xff $@
 PAD_hrom	= $(PAD_rom)
-PAD_xrom	= $(PAD_rom)
 PAD_dsk		= $(PADIMG) --blksize=512 $@
 PAD_hd		= $(PADIMG) --blksize=32768 $@