Remove references to unused symbols

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1545 42af7a65-404d-4744-a932-0658087f49c3

arch/z80/src/z8/z8_head.S

@@ -69,11 +69,6 @@
 	xref	_z16f_lowinit:ROM
 #ifdef CONFIG_ARCH_LEDS
 	xref	_up_ledinit:ROM
-#endif
-#if defined(CONFIG_USE_LOWUARTINIT)
-	xref	_z16f_lowuartinit:ROM
-#elif defined(CONFIG_USE_EARLYSERIALINIT)
-	xref	_up_earlyserialinit:ROM
 #endif
 	xref	_os_start:ROM
 	xref	_up_doirq:ROM