xtensa: ptrace: add prototypes to <asm/ptrace.h>

Add prototype for do_syscall_trace_enter() to asm/ptrace.h.
Move prototype for do_syscall_trace_leave() there to be consistent.

Fixes a build warning:

arch/xtensa/kernel/ptrace.c:545:5: warning: no previous prototype for 'do_syscall_trace_enter' [-Wmissing-prototypes]
  545 | int do_syscall_trace_enter(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: <20230920052139.10570-5-rdunlap@infradead.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>