lib: Remove string from parman config selection

As reported by Geert, remove the string so the user does not see this
config option. The option is explicitly selected only as a dependency of
in-kernel users.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Fixes: 44091d29 ("lib: Introduce priority array area manager")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: David S. Miller <davem@davemloft.net>