Introduce some macros and helpers to avoid magic numbers and
rename macros/functions for clarification.

- We see '| 2' in several places.  This means Data Cycle in MAP11 mode.
  The Denali User's Guide says bit[1:0] of MAP11 is like follows:

  b'00 = Command Cycle
  b'01 = Address Cycle
  b'10 = Data Cycle

  So, this commit added DENALI_MAP11_{CMD,ADDR,DATA} macros.

- We see 'denali->flash_mem + 0x10' in several places, but 0x10 is a
  magic number.  Actually, this accesses the data port of the Host
  Data/Command Interface.  So, this commit added DENALI_HOST_DATA.
  On the other hand, 'denali->flash_mem' gets access to the address
  port, so DENALI_HOST_ADDR was also added.

- We see 'index_addr(denali, cmd, 0x1)' in denali_erase(), but 0x1
  is a magic number.  0x1 means the erase operation.  Replace 0x1
  with DENALI_ERASE.

- Rename index_addr() to denali_host_write() for clarification

- Denali User's Guide says MAP{00,01,10,11} for access mode.  Match
  the macros with terminology in the IP document.

- Rename struct members as follows:
  flash_bank   -> active_bank    (currently selected bank)
  flash_reg    -> reg            (base address of registers)
  flash_mem    -> host           (base address of host interface)
  devnum       -> devs_per_cs    (devices connected in parallel)
  bbtskipbytes -> oob_skip_bytes (number of bytes to skip in OOB)
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>