Sorting include files in alphabetic order in
drivers/tty/serial/samsung.c revealed the following error:

In file included from drivers/tty/serial/samsung_tty.c:24:
./arch/arm64/include/asm/irq.h:9:43: error: unknown type name ‘cpumask_t’
    9 | void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu);
      |                                           ^~~~~~~~~

Include cpumask.h to avoid unknown type errors for parents of irq.h that
don't include cpumask.h.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20240110074007.4020016-1-tudor.ambarus@linaro.orgSigned-off-by: Will Deacon <will@kernel.org>