hw/mips: implement ITC Configuration Tags and Storage Cells

hw/mips: implement ITC Configuration Tags and Storage Cells

Implement ITC as a single object consisting of two memory regions:

1) tag_io: ITC Configuration Tags (i.e. ITCAddressMap{0,1} registers) which
are accessible by the CPU via CACHE instruction. Also adding
MemoryRegion *itc_tag to the CPUMIPSState so that CACHE instruction will
dispatch reads/writes directly.

2) storage_io: memory-mapped ITC Storage whose address space is configurable
(i.e. enabled/remapped/resized) by writing to ITCAddressMap{0,1} registers.

ITC Storage contains FIFO and Semaphore cells. Read-only FIFO bit in the
ITC cell tag indicates the type of the cell. If the ITC Storage contains
both types of cells then FIFOs are located before Semaphores.

Since issuing thread can get blocked on the access to a cell (in E/F
Synchronized and P/V Synchronized Views) each cell has a bitmap to track
which threads are currently blocked.

Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>