arm64: cpufeature: Fix typos in comment

Fix up one typos: CTR_E0 -> CTR_EL0

Cc: Will Deacon <will@kernel.org>
Acked-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>