[legacy] Allocate legacy driver .bss-like segments at probe time

Some legacy drivers use large static allocations for transmit and
receive buffers.  To avoid bloating the .bss segment, we currently
implement these as a single common symbol named "_shared_bss" (which
is permissible since only one legacy driver may be active at any one
time).

Switch to dynamic allocation of these .bss-like segments, to avoid the
requirement for using common symbols.

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

src/drivers/net/3c509-eisa.c

@@ -35,7 +35,7 @@ static struct eisa_device_id el3_eisa_adapters[] = {
 EISA_DRIVER ( el3_eisa_driver, el3_eisa_adapters );
 
 DRIVER ( "3c509 (EISA)", nic_driver, eisa_driver, el3_eisa_driver,
-	 el3_eisa_probe, el3_eisa_disable );
+	 el3_eisa_probe, el3_eisa_disable, no_fake_bss );
 
 ISA_ROM ( "3c509-eisa","3c509 (EISA)" );