arm64: cpufeature: Remove duplicate asm/mmu.h header

./arch/arm64/kernel/cpufeature.c: asm/mmu.h is included more than once.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Will Deacon <will@kernel.org>