x86/entry/fred: Push __KERNEL_CS directly

Push __KERNEL_CS directly, rather than moving it into RAX and then
pushing RAX.

No functional changes.

Suggested-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250822071644.1405268-1-xin@zytor.com

Author: xinli-intel

arch/x86/entry/entry_64_fred.S

@@ -97,8 +97,7 @@ SYM_FUNC_START(asm_fred_entry_from_kvm)
 	push %rdi			/* fred_ss handed in by the caller */
 	push %rbp
 	pushf
-	mov $__KERNEL_CS, %rax
-	push %rax
+	push $__KERNEL_CS
 
 	/*
 	 * Unlike the IDT event delivery, FRED _always_ pushes an error code