x86/microcode: Do not upload microcode if CPUs are offline

x86/microcode: Do not upload microcode if CPUs are offline

Avoid loading microcode if any of the CPUs are offline, and issue a
warning. Having different microcode revisions on the system at any time
is outright dangerous.

[ Borislav: Massage changelog. ]

Signed-off-by: Ashok Raj <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Tom Lendacky <[email protected]>
Tested-by: Ashok Raj <[email protected]>
Reviewed-by: Tom Lendacky <[email protected]>
Cc: Arjan Van De Ven <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]