efi/libstub: Use %ls for filename

efi_printk can now handle the UTF-16 filename, so print it using efi_err
instead of a separate efi_char16_puts call.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200518190716.751506-23-nivedita@alum.mit.edu


Signed-off-by: Ard Biesheuvel <ardb@kernel.org>