arm64: debug: consolidate software breakpoint handlers

arm64: debug: consolidate software breakpoint handlers

The software breakpoint handlers are hooked in directly from ptrace,
which makes it difficult to add additional handlers for things like
kprobes and kgdb.

This patch moves the handling code into debug-monitors.c, where we can
dispatch to different debug subsystems more easily.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 1442b6ed249d2b3d2cfcf45b65ac64393495c96c)
Signed-off-by: Mark Brown <broonie@linaro.org>