MIPS: Remove dead case label.

CPU_CAVIUM_OCTEON is mips_r2 which is handled before the switch.  This
label in the switch statement is dead code, so we remove it.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Reviewed by: David VomLehn <dvomlehn@cisco.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>