init: make unknown command line param message clearer

The prior message is confusing users, which is the exact opposite of the
goal.  If the message is being seen, one of the following situations is
happening:

 1. the param is misspelled
 2. the param is not valid due to the kernel configuration
 3. the param is intended for init but isn't after the '--'
    delineator on the command line

To make that more clear to the user, explicitly mention "kernel command
line" and also note that the params are still passed to user space to
avoid causing any alarm over params intended for init.

Link: https://lkml.kernel.org/r/20211013223502.96756-1-ahalaney@redhat.com


Fixes: 86d1919a ("init: print out unknown kernel parameters")
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>