remove obsolete symbols in a single environment

arch/x86/kernel/entry64.asm

@@ -96,6 +96,7 @@ boot_pt times (NOPTS*512) DQ 0
 
 SECTION .text
 ALIGN 8
+%if MAX_CORES > 1
 global smp_entry
 smp_entry:
 ; enable caching, disable paging and fpu emulation
@@ -136,6 +137,7 @@ smp_entry:
     jmp GDT64.Code:smp_start64 ; Set the code segment and enter 64-bit long mode.
 
     jmp $ ; endless loop
+%endif
 
 search_apic:
     push ebp
@@ -369,6 +371,7 @@ start64:
     call main
     jmp $
 
+%if MAX_CORES > 1
 smp_start64:
 ; initialize segment registers
     mov ax, GDT64.Data
@@ -382,6 +385,7 @@ smp_start64:
     extern smp_start
     call smp_start
     jmp $
+%endif
 
 global cpu_init
 cpu_init: