ELF: fix all "Elf" typos

ELF is acronym and therefore should be spelled in all caps.

I left one exception at Documentation/arm/nwfpe/nwfpe.rst which looks like
being written in the first person.

Link: https://lkml.kernel.org/r/Y/3wGWQviIOkyLJW@p183
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/arch/um/os-Linux/elf_aux.c b/arch/um/os-Linux/elf_aux.c
index 77a9321..344ac40 100644
--- a/arch/um/os-Linux/elf_aux.c
+++ b/arch/um/os-Linux/elf_aux.c
@@ -2,7 +2,7 @@
 /*
  *  arch/um/kernel/elf_aux.c
  *
- *  Scan the Elf auxiliary vector provided by the host to extract
+ *  Scan the ELF auxiliary vector provided by the host to extract
  *  information about vsyscall-page, etc.
  *
  *  Copyright (C) 2004 Fujitsu Siemens Computers GmbH