MEM: Move all read/write blob functions from Port to PortProxy

This patch moves the readBlob/writeBlob/memsetBlob from the Port class
to the PortProxy class, thus making a clear separation of the basic
port functionality (recv/send functional/atomic/timing), and the
higher-level functional accessors available on the port proxies.

There are only a few places in the code base where the blob functions
were used on ports, and they are all for peeking into the memory
system without making a normal memory access (in the memtest, and the
malta and tsunami pchip). The memtest also exemplifies how easy it is
to create a non-translating proxy if desired. The malta and tsunami
pchip used a slave port to perform a functional read, and this is now
changed to rely on the physProxy of the system (to which they already
have a pointer).

src/mem/SConscript

@@ -41,6 +41,7 @@ Source('mport.cc')
 Source('packet.cc')
 Source('port.cc')
 Source('tport.cc')
+Source('port_proxy.cc')
 Source('fs_translating_port_proxy.cc')
 Source('se_translating_port_proxy.cc')