Docs: Improve docs on boot parameters dodmraid[=...] and scandelay[=...]

doc/genkernel.8.txt

@@ -394,8 +394,8 @@ which the ramdisk scripts would recognize.
     software,  and in case your encrypted device isn't open with the
     key, it opens a shell in the initrd quietly.
 
-*dodmraid*=<...>::
+*dodmraid*[=<...>]::
-    Passes arguments to dmraid on bootup.
+    Activate Device-Mapper RAID and (optionally) pass arguments to it.
 
 *real_init*=<...>::
     Override location of init script, default is "/sbin/init".
@@ -403,7 +403,7 @@ which the ramdisk scripts would recognize.
 *init_opts*=<...>::
     Passes arguments to init on bootup.
 
-*scandelay*=<...>::
+*scandelay*[=<...>]::
     Pauses for 10 seconds before running devfsd if no argument is
     specified; otherwise pauses for the number of specified seconds.