MIPS: Remove deprecated CONFIG_MIPS_CMP

Commit 5cac93b3 ("MIPS: Deprecate CONFIG_MIPS_CMP") deprecated
CONFIG_MIPS_CMP and after 9 years it's time to remove it.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>