xtensa: fault: include <asm/traps.h>

Use <asm/traps.h> to provide the function prototype for do_page_fault()
to prevent a build warning:

arch/xtensa/mm/fault.c:87:6: warning: no previous prototype for 'do_page_fault' [-Wmissing-prototypes]
   87 | void do_page_fault(struct pt_regs *regs)

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Message-Id: <20230920052139.10570-3-rdunlap@infradead.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>