MIPS: Octeon: Guard the Kconfig body with CPU_CAVIUM_OCTEON

Instead of making each Octeon specific option depend on
CPU_CAVIUM_OCTEON, gate the body of the entire file with
CPU_CAVIUM_OCTEON.  With this change, CAVIUM_OCTEON_SPECIFIC_OPTIONS
becomes useless, so get rid of it as well.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2091/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>