dummy_lproc: add the basic IPI functionality

Use the standard APIC IPI and 2 vectors (from/to BSP) - for debug purposes
(we can easily fit into 1).

Also, if BSP is kicked - find struct rproc *, so that we can use the data
behind it.

Signed-off-by: Veaceslav Falico <vfalico@gmail.com>