efi: Export efi_query_variable_store() for efivars.ko

Fixes build with CONFIG_EFI_VARS=m which was broken after the commit
"x86, efivars: firmware bug workarounds should be in platform code".

Signed-off-by: Sergey Vlasov <vsu@altlinux.ru>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

arch/x86/platform/efi/efi.c

@@ -1144,3 +1144,4 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
 
 	return EFI_SUCCESS;
 }
+EXPORT_SYMBOL_GPL(efi_query_variable_store);