powerpc/setup_64: Fix sparse warnings

Sparse warns:
  warning: symbol 'rfi_flush' was not declared.
  warning: symbol 'entry_flush' was not declared.
  warning: symbol 'uaccess_flush' was not declared.

Define 'entry_flush' and 'uaccess_flush' as static because they are
not referenced outside the file. Include asm/security_features.h in
which 'rfi_flush' is declared.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: He Ying <heying24@huawei.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210316041148.29694-1-heying24@huawei.com

arch/powerpc/kernel/setup_64.c

@@ -50,6 +50,7 @@
 #include <asm/setup.h>
 #include <asm/rtas.h>
 #include <asm/iommu.h>
+#include <asm/security_features.h>
 #include <asm/serial.h>
 #include <asm/cache.h>
 #include <asm/page.h>
@@ -949,8 +950,8 @@ static bool no_rfi_flush;
 static bool no_entry_flush;
 static bool no_uaccess_flush;
 bool rfi_flush;
-bool entry_flush;
-bool uaccess_flush;
+static bool entry_flush;
+static bool uaccess_flush;
 DEFINE_STATIC_KEY_FALSE(uaccess_flush_key);
 EXPORT_SYMBOL(uaccess_flush_key);