ACPI: CPPC: Fix NULL pointer dereference when nosmp is used

In the Linux kernel, the following vulnerability has been resolved:

ACPI: CPPC: Fix NULL pointer dereference when nosmp is used

With nosmp in cmdline, other CPUs are not brought up, leaving

their cpc_desc_ptr NULL. CPU0's iteration via for_each_possible_cpu()

dereferences these NULL pointers, causing panic.

Panic backtrace:

[ 0.401123] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000b8

...

[ 0.403255] [<ffffffff809a5818>] cppc_allow_fast_switch+0x6a/0xd4

...

Kernel panic - not syncing: Attempted to kill init!

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