Indirect access to source and priority configuration

[mark-honman]

with reference to section 3.2 "Indirect access to APLIC registers".

Suggest renaming to make clear that there is no APLIC.

Rather say something like:

• The ACLIC provides interrupt source and priority configuration capabilities as defined for the APLIC, except that when the source configuration Delegate bit is set, bits 9:0 identify the ACLIC interrupt file to which the interrupt is delegated. [or perhaps it is just a mode-delegation...]
• As with AIA hart-local interrupt pending and enable registers, the interrupt source and priority configuration are provided with an indirect CSR interface.

[mark-honman]

Since these indirectly-accessible registers align with IMSIC-like interrupt files in the ACLIC, register naming and address conventions should also align. However it's not clear whether there is a gap in CSRind space after the previously defined AIA indirect CSRs.

[mark-honman]

Proposed rename of section to "Indirect CSR access to ACLIC source and priority configuration registers"