x86/percpu: Fix x86_this_cpu_variable_test_bit() asm template

Fix x86_this_cpu_variable_test_bit(), which is implemented with an
incorrect asm template, where argument 2 (count argument) is considered
a percpu variable. However, x86_this_cpu_test_bit() is currently
used exclusively with constant bit number argument, so the called
x86_this_cpu_variable_test_bit() function is never instantiated.

The fix introduces named assembler operands to prevent this kind
of error.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20240404094218.448963-1-ubizjak@gmail.com

arch/x86/include/asm/percpu.h

@@ -586,10 +586,11 @@ static inline bool x86_this_cpu_variable_test_bit(int nr,
 {
 	bool oldbit;
 
-	asm volatile("btl "__percpu_arg(2)",%1"
+	asm volatile("btl %[nr], " __percpu_arg([var])
 			CC_SET(c)
 			: CC_OUT(c) (oldbit)
-			: "m" (*__my_cpu_ptr((unsigned long __percpu *)(addr))), "Ir" (nr));
+			: [var] "m" (*__my_cpu_ptr((unsigned long __percpu *)(addr))),
+			  [nr] "Ir" (nr));
 
 	return oldbit;
 }