efi/libstub: Rename efi_[char16_]printk to efi_[char16_]puts

These functions do not support formatting, unlike printk. Rename them to
puts to make that clear.

Move the implementations of these two functions next to each other.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200518190716.751506-3-nivedita@alum.mit.edu


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