MIPS: uprobes: fix incorrect uprobe brk handling

MIPS: uprobes: fix incorrect uprobe brk handling

When a uprobe-replacement breakpoint instruction is handled, a notifier
is called with DIE_UPROBE argument, but a corresponding exception notify
handler for MIPS attempts to handle DIE_BREAK instead. As a result
the breakpoint instruction isn't handled by the uprobe code and the probed
application terminates with SIGTRAP.
Fix this by changing arch_uprobe_exception_notify code to handle
DIE_UPROBE as a pre-singlestep condition instead of DIE_BREAK.

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13884/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>