efi: app: Provide easy access to runtime services

Add a function which allows the app to obtain the runtime services
without first obtaining the priv data.

Make use of this in efi_vars.c

Signed-off-by: Simon Glass <sjg@chromium.org>

include/efi.h

@@ -604,6 +604,13 @@ struct efi_system_table *efi_get_sys_table(void);
  */
 struct efi_boot_services *efi_get_boot(void);
 
+/**
+ * efi_get_run() - Get access to the EFI runtime-services table
+ *
+ * Returns: pointer to EFI runtime-services table
+ */
+struct efi_runtime_services *efi_get_run(void);
+
 /**
  * efi_get_parent_image() - Get the handle of the parent image
  *