AMBA AHB Bus Manager

[rishyak]

The manager should:

• Initiate read and write operations
• Provide address and control information to the relevant subordinate

AHB spec says:

An AHB bus manager has the most complex bus interface in an AMBA system. Typically an AMBA system designer would use predesigned bus managers and therefore would not need to be concerned with the detail of the bus master interface.

We are not using a predesigned bus manager, and we need to implement this as we see fit.

[rishyak]

This also needs to be split into multiple parts and triaged.

[rishyak]

@kevincyap @kc3977 sit with me next week, I want to make some decisions about the manager's behaviour with burst transfers. This will affect how the subordinates deal with burst transfers too.