xtensa: smp: add headers for missing function prototypes

Use <asm/smp.h> to provide the prototype for secondary_start_kernel().
Use <linux/profile.h> to provide the prototype for
setup_profiling_timer().

arch/xtensa/kernel/smp.c:119:6: warning: no previous prototype for 'secondary_start_kernel' [-Wmissing-prototypes]
  119 | void secondary_start_kernel(void)
arch/xtensa/kernel/smp.c:461:5: warning: no previous prototype for 'setup_profiling_timer' [-Wmissing-prototypes]
  461 | int setup_profiling_timer(unsigned int multiplier)

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Message-Id: <20230920052139.10570-11-rdunlap@infradead.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>