efi/printf: Drop %n format and L qualifier

%n is unused and deprecated.

The L qualifer is parsed but not actually implemented.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200518190716.751506-7-nivedita@alum.mit.edu


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