[fix] Realign addresses to 64-bit

[creinwar]

The read/write logic in dm_mem.sv only looks at the request address and does not take the byte strobes into account which causes problems when trying to write the Halted, Going, Resuming and Exception locations from a bus that is larger than 32 bit as that would require misaligned requests. This PR addresses this by realigning the relevant addresses to 64 bits, which makes the DM work for 32 and 64-bit harts.

[bluewww]

I'll double check otherwise looks good. Could you also please update the documentation (it describes the debug module addresses).