kernel_debugger_core: add interrupt-context debugger core

kernel_debugger_core: add interrupt-context debugger core

This provides kernel_debugger() which can be called from an interrupt
context low level debugger wedge to execute commands that inspect
kernel state.  It doesn't do much on its own.

Signed-off-by: Brian Swetland <swetland@google.com>
kernel_debugger_core: Add sysrq command.

sysrq <c> will run the sysrq command <c> and dump what
was added to the kernel log while the command ran.

Signed-off-by: Brian Swetland <swetland@google.com>
Signed-off-by: Arve Hjønnevåg <arve@android.com>