x86/entry: Compile entry_SYSCALL32_ignore() unconditionally

jira VULN-772
cve-pre CVE-2024-25744
commit-author Nikolay Borisov <nik.borisov@suse.com>
commit 370dcd5

To limit the IA32 exposure on 64bit kernels while keeping the
flexibility for the user to enable it when required, the compile time
enable/disable via CONFIG_IA32_EMULATION is not good enough and will
be complemented with a kernel command line option.

Right now entry_SYSCALL32_ignore() is only compiled when
CONFIG_IA32_EMULATION=n, but boot-time enable- / disablement obviously
requires it to be unconditionally available.

Remove the #ifndef CONFIG_IA32_EMULATION guard.

	Signed-off-by: Nikolay Borisov <nik.borisov@suse.com>
	Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230623111409.3047467-4-nik.borisov@suse.com

(cherry picked from commit 370dcd5)
	Signed-off-by: Marcin Wcisło <marcin.wcislo@conclusive.pl>

Author: pvts-mat

arch/x86/entry/entry_64.S

@@ -1498,7 +1498,6 @@ nmi_restore:
 	iretq
 SYM_CODE_END(asm_exc_nmi)
 
-#ifndef CONFIG_IA32_EMULATION
 /*
  * This handles SYSCALL from 32-bit code.  There is no way to program
  * MSRs to fully disable 32-bit SYSCALL.
@@ -1509,7 +1508,6 @@ SYM_CODE_START(entry_SYSCALL32_ignore)
 	mov	$-ENOSYS, %eax
 	sysretl
 SYM_CODE_END(entry_SYSCALL32_ignore)
-#endif
 
 .pushsection .text, "ax"
 SYM_CODE_START(rewind_stack_and_make_dead)