x86/unwind_user: Simplify unwind_user_word_size()

Get rid of superfluous ifdef and return explicit word size depending on
32-bit or 64-bit mode.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251208160352.1363040-5-jremus@linux.ibm.com

arch/x86/include/asm/unwind_user.h

@@ -12,11 +12,7 @@ static inline int unwind_user_word_size(struct pt_regs *regs)
 	/* We can't unwind VM86 stacks */
 	if (regs->flags & X86_VM_MASK)
 		return 0;
-#ifdef CONFIG_X86_64
-	if (!user_64bit_mode(regs))
-		return sizeof(int);
-#endif
-	return sizeof(long);
+	return user_64bit_mode(regs) ? 8 : 4;
 }
 
 #endif /* CONFIG_UNWIND_USER */