Most architectures have been passing the location of an initrd via the
initrd= option since their inception.  Remove the comment as it's both
wrong and unrelated to the commit that introduced it.

For a bit more context, I assume there's been some confusion between
"initrd" being a keyword in things like extlinux.conf and also that for
quite a long time now initrd information is passed via device tree and
not the command line on relevant architectures. But it's still true that
it's been a valid command line option to the kernel since the 90s. It's
just the case that in 2018 the code was consolidated from under arch/
and in to this file.

 [ bp: Move the context clarification up into the commit message proper. ]

Fixes: 694cfd87 ("x86/setup: Add an initrdmem= option to specify initrd physical address")
Signed-off-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200619143056.24538-1-trini@konsulko.com