x86/callthunks: Use EXPORT_PER_CPU_SYMBOL_GPL() for per CPU variables

Sparse complains rightfully about the usage of EXPORT_SYMBOL_GPL() for per
CPU variables:

  callthunks.c:346:20: sparse: warning: incorrect type in initializer (different address spaces)
  callthunks.c:346:20: sparse:    expected void const [noderef] __percpu *__vpp_verify
  callthunks.c:346:20: sparse:    got unsigned long long *

Use EXPORT_PER_CPU_SYMBOL_GPL() instead.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240304005104.841915535@linutronix.de

arch/x86/kernel/callthunks.c

@@ -42,8 +42,8 @@ DEFINE_PER_CPU(u64, __x86_call_count);
 DEFINE_PER_CPU(u64, __x86_ret_count);
 DEFINE_PER_CPU(u64, __x86_stuffs_count);
 DEFINE_PER_CPU(u64, __x86_ctxsw_count);
-EXPORT_SYMBOL_GPL(__x86_ctxsw_count);
-EXPORT_SYMBOL_GPL(__x86_call_count);
+EXPORT_PER_CPU_SYMBOL_GPL(__x86_ctxsw_count);
+EXPORT_PER_CPU_SYMBOL_GPL(__x86_call_count);
 #endif
 
 extern s32 __call_sites[], __call_sites_end[];