It turns out the number of banks can be extended past 8 if the system
has an 80 GB HDD, though repartitioning will be needed in order to take
full advantage of this, since the bank table will extend into the start
of Bank 1.
[librvth] nhcd_structs.h: Updated `NHCD_BankTable_Header`.
[librvth] rvth.c: Renamed `RvtH.banks` to `RvtH.bank_count`.
`magic` and `type` are still kept as char[4] for ease of explanation.
They're uint32_t in nhcd_structs.h to allow for it to be checked using
a single compare instruction.
