x86/cpu: Use EXPORT_PER_CPU_SYMBOL_GPL() for x86_spec_ctrl_current

Sparse rightfully complains:

  bugs.c:71:9: sparse: warning: incorrect type in initializer (different address spaces)
  bugs.c:71:9: sparse:    expected void const [noderef] __percpu *__vpp_verify
  bugs.c:71:9: sparse:    got unsigned long long *

The reason is that x86_spec_ctrl_current which is a per CPU variable is
exported with EXPORT_SYMBOL_GPL().

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/20240304005104.732288812@linutronix.de

arch/x86/kernel/cpu/bugs.c

@@ -56,7 +56,7 @@ EXPORT_SYMBOL_GPL(x86_spec_ctrl_base);
 
 /* The current value of the SPEC_CTRL MSR with task-specific bits set */
 DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
-EXPORT_SYMBOL_GPL(x86_spec_ctrl_current);
+EXPORT_PER_CPU_SYMBOL_GPL(x86_spec_ctrl_current);
 
 u64 x86_pred_cmd __ro_after_init = PRED_CMD_IBPB;
 EXPORT_SYMBOL_GPL(x86_pred_cmd);