efi/x86: Fix cast of image argument

handle_protocol() expects void **, not void *.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200305143642.820865-1-nivedita@alum.mit.edu
Link: https://lore.kernel.org/r/20200308080859.21568-28-ardb@kernel.org