powerpc/pseries: Make symbol '__pcpu_scope_hcall_stats' static

The sparse tool complains as follows:

arch/powerpc/platforms/pseries/hvCall_inst.c:29:1: warning:
 symbol '__pcpu_scope_hcall_stats' was not declared. Should it be static?

This symbol is not used outside of hvCall_inst.c, so this
commit marks it static.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Bixuan Cui <cuibixuan@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210409090109.59347-1-cuibixuan@huawei.com

arch/powerpc/platforms/pseries/hvCall_inst.c

@@ -26,7 +26,7 @@ struct hcall_stats {
 };
 #define HCALL_STAT_ARRAY_SIZE	((MAX_HCALL_OPCODE >> 2) + 1)
 
-DEFINE_PER_CPU(struct hcall_stats[HCALL_STAT_ARRAY_SIZE], hcall_stats);
+static DEFINE_PER_CPU(struct hcall_stats[HCALL_STAT_ARRAY_SIZE], hcall_stats);
 
 /*
  * Routines for displaying the statistics in debugfs