x86/ucode: Fix error paths control_thread_fn()

x86/ucode: Fix error paths control_thread_fn()

These two early exits skipped re-enabling the watchdog, restoring the NMI
callback, and clearing the nmi_patch global pointer.  Always execute the tail
of the function on the way out.

Fixes: 8dd4dfa92d62 ("x86/microcode: Synchronize late microcode loading")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: fc2e1f3aad602a66c14b8285a1bd38a82f8fd02d
master date: 2023-03-28 11:57:56 +0100