[fix] warning: use of deprecated item: prefer using indexing

[errordeveloper]

Fixing this in just the src/hal/lpc17xx/pin_pt.rs first results in:

error: mismatched types: expected `core::option::Option<std::collections::hashmap::HashMap<collections::string::String,uint>>` but found an `&`-pointer pattern

Fixing the above error, gives this:

error: cannot move out of dereference (dereference is implicit, due to indexing)

[farcaller]

Indexing is back, awesome!