arm64: cpufeature: Fix mismerge of CONFIG_ARM64_SSBD block

When merging support for SSBD and the CRC32 instructions, the conflict
resolution for the new capability entries in arm64_features[]
inadvertedly predicated the availability of the CRC32 instructions on
CONFIG_ARM64_SSBD, despite the functionality being entirely unrelated.

Move the #ifdef CONFIG_ARM64_SSBD down so that it only covers the SSBD
capability.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>