c6x: defconfig: Cleanup from old Kconfig options

Remove old, dead Kconfig options (in order appearing in this commit):
 - EXPERIMENTAL is gone since v3.9;
 - MISC_DEVICES: commit 7c5763b8

 ("drivers: misc: Remove
   MISC_DEVICES config option");

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Mark Salter <msalter@redhat.com>