efi: Rename efi_early_memdesc_ptr() to efi_memdesc_ptr()

The "early" part of the helper's name isn't accurate[1]. Drop it in
preparation for adding a new (not early) usage.

Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/lkml/CAMj1kXEyDjH0uu3Z4eBesV3PEnKGi5ArXXMp7R-hn8HdRytiPg@mail.gmail.com

 [1]
Signed-off-by: Kees Cook <kees@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>