hexagon: Fix function name in die()

When building ARCH=hexagon defconfig:

arch/hexagon/kernel/traps.c:217:2: error: implicit declaration of
function 'make_dead_task' [-Werror,-Wimplicit-function-declaration]
        make_dead_task(err);
        ^

The function's name is make_task_dead(), change it so there is no more
build error.

Fixes: 0e25498f

 ("exit: Add and use make_task_dead.")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lkml.kernel.org/r/20211227184851.2297759-2-nathan@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>