microblaze: Fix sparse warnings - ptrace

Warning log:
CHECK   arch/microblaze/kernel/ptrace.c
arch/microblaze/kernel/ptrace.c:126:11: warning: incorrect type in initializer (different address spaces)
arch/microblaze/kernel/ptrace.c:126:11:    expected unknown type 2[noderef] *__pu_addr<asn:1>
arch/microblaze/kernel/ptrace.c:126:11:    got unsigned long *<noident>
arch/microblaze/kernel/ptrace.c:134:17: warning: symbol 'do_syscall_trace_enter' was not declared. Should it be static?
arch/microblaze/kernel/ptrace.c:157:17: warning: symbol 'do_syscall_trace_leave' was not declared. Should it be static?

Signed-off-by: Michal Simek <monstr@monstr.eu>