MIPS: Remove set_swbp() in uprobes.c

set_swbp() in arch/mips/kernel/uprobes.c is same with the weak version
in kernel/events/uprobes.c, remove it.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>