x86/speculation: Remove Skylake C2 from Speculation Control microcode blacklist

x86/speculation: Remove Skylake C2 from Speculation Control microcode blacklist

In accordance with Intel's microcode revision guidance from March 6 MCU
rev 0xc2 is cleared on both Skylake H/S and Skylake Xeon E3 processors
that share CPUID 506E3.

Signed-off-by: Alexander Sergeyev <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Jia Zhang <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Kyle Huey <[email protected]>
Cc: David Woodhouse <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]