ash: explicltly group ash options

ash: explicltly group ash options

This would makes all ash options indented inside "ash" in menuconfig.
It appears that menuconfig has a limit at tracking multiple dependency
lines like this (it looks like a "diamond problem" but I'm not sure if
it is):

               ---ASH <----------
              /                  \       ASH_OPTIMIZE_FOR_SIZE
    !NOMMU <-*----SH_IS_ASH <----[OR] <--ASH_INTERNAL_GLOB
              \                  /       ASH_RANDOM_SUPPORT
               ---BASH_IS_ASH <--        [...]

The kconfig-language document [1] states that:

> If a menu entry somehow depends on the previous entry, it can be
> made a submenu of it. First, the previous (parent) symbol must be
> part of the dependency list and then one of these two conditions
> must be true:
> - the child entry must become invisible, if the parent is set to 'n'

    [BusyBox ash used to satisfy this, but no longer does]

> - the child entry must only be visible, if the parent is visible

    [BusyBox ash configs actually satisfy this, but because of
     "diamond" above this might not be easily detected]

So I found out a direct workaround: by making ash options explicitly
depend on !NOMMU, we can tell menuconfig that rule 2 above is satisfied
without any more tracking.

               ---------------------
              /                     \
    !NOMMU <-*-----ASH <--------     \
              \                 \     \        ASH_OPTIMIZE_FOR_SIZE
               *---SH_IS_ASH <---[OR]-[AND] <--ASH_INTERNAL_GLOB
                \                /             ASH_RANDOM_SUPPORT
                 --BASH_IS_ASH <-              [...]

So all ash options would now be indented under "ash".

[1] "Documentation/kbuild/kconfig-language.txt" in Linux kernel source

Signed-off-by: Kang-Che Sung <explorer09@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>