tests/kernel/smp: Correct parameter name

The k_sys_fatal_error_handler() function is declared in zephyr/fatal.h
with a name of "esf" for the second parameter, not "pEsf".  For
unknown reasons, this is showing up in CI as a documentation
generation failure pointing at the (correct) header.

Still, no reason not to synchronize.

Signed-off-by: Andy Ross <andyross@google.com>