MIPS: Octeon: Delete override of cpu_has_mips_r2_exec_hazard.

This is no longer needed with the fixed, new and improved definition
of cpu_has_mips_r2_exec_hazard in <asm/cpu-features.h>.

For a discussion, see http://patchwork.linux-mips.org/patch/9539/

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Signed-off-by: Ralf Baechle <ralf@linux-mips.org>