arm64: kprobes: Move extable address check into arch_prepare_kprobe()

Move extable address check into arch_prepare_kprobe() from
arch_within_kprobe_blacklist().
The blacklist is exposed via debugfs as a list of symbols.
The extable entries are smaller, so must be filtered out
by arch_prepare_kprobe().

Acked-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>