hexagon: time: include asm/time.h for prototypes

hexagon: time: include asm/time.h for prototypes

Clang warns about missing prototypes that are declared in this header:

  arch/hexagon/kernel/time.c:118:6: warning: no previous prototype for function 'setup_percpu_clockdev' [-Wmissing-prototypes]
    118 | void setup_percpu_clockdev(void)
        |      ^
  arch/hexagon/kernel/time.c:118:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
    118 | void setup_percpu_clockdev(void)
        | ^
        | static
  arch/hexagon/kernel/time.c:135:6: warning: no previous prototype for function 'ipi_timer' [-Wmissing-prototypes]
    135 | void ipi_timer(void)
        |      ^
  arch/hexagon/kernel/time.c:135:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
    135 | void ipi_timer(void)
        | ^
        | static

Link: https://lkml.kernel.org/r/20231130-hexagon-missing-prototypes-v1-8-5c34714afe9e@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>