docs: alphabetize entries in kernel-parameters.txt

Move entries to be in alpha order as specified near the beginning
of this file.

Clean up some whitespace and line-length miscues.

Add '=' to "selinux" option syntax.
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>