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>
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 4959e3f..4f364c7 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -1144,3 +1144,4 @@
 
 	return EFI_SUCCESS;
 }
+EXPORT_SYMBOL_GPL(efi_query_variable_store);