hexagon: smp: mark handle_ipi() and start_secondary() as static

hexagon: smp: mark handle_ipi() and start_secondary() as static

Clang warns:

  arch/hexagon/kernel/smp.c:82:13: warning: no previous prototype for function 'handle_ipi' [-Wmissing-prototypes]
     82 | irqreturn_t handle_ipi(int irq, void *desc)
        |             ^
  arch/hexagon/kernel/smp.c:82:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
     82 | irqreturn_t handle_ipi(int irq, void *desc)
        | ^
        | static
  arch/hexagon/kernel/smp.c:127:6: warning: no previous prototype for function 'start_secondary' [-Wmissing-prototypes]
    127 | void start_secondary(void)
        |      ^
  arch/hexagon/kernel/smp.c:127:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
    127 | void start_secondary(void)
        | ^
        | static
  2 warnings generated.

These functions are not used outside of this translation unit, so mark
them as static.

Link: https://lkml.kernel.org/r/20231130-hexagon-missing-prototypes-v1-4-5c34714afe9e@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Brian Cain <bcain@quicinc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>