x86: fix trampoline stack clobber

We need to lock interrupts before setting the thread's
stack pointer to the trampoline stack. Otherwise, we
could unexpectedly take an interrupt on this stack
instead of the thread stack as intended.

The specific problem happens at the end of the interrupt,
when we switch back to the thread stack and call swap.
Doing this on a per-cpu trampoline stack instead of the
thread stack causes data corruption.

Fixes: #24869

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>