x86/cpu/bugs: Use __initconst for 'const' init data

Some of the recently added const tables use __initdata which causes section
attribute conflicts.

Use __initconst instead.

Fixes: fa1202ef

 ("x86/speculation: Add command line control")
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20190330004743.29541-9-andi@firstfloor.org