hw/block/pflash_cfi02: Rename register_memory(true) as mode_read_array

hw/block/pflash_cfi02: Rename register_memory(true) as mode_read_array

The same pattern is used when setting the flash in READ_ARRAY mode:
- Set the state machine command to READ_ARRAY
- Reset the write_cycle counter
- Reset the memory region in ROMD

Refactor the current code by extracting this pattern.
It is used three times:

- When the timer expires and not in bypass mode

- On a read access (on invalid command).

- When the device is initialized. Here the ROMD mode is hidden
  by the memory_region_init_rom_device() call.

pflash_register_memory(rom_mode=true) already sets the ROM device
in "read array" mode (from I/O device to ROM one). Explicit that
by renaming the function as pflash_mode_read_array(), adding
a trace event and resetting wcycle.

Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: David Edmondson <david.edmondson@oracle.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210310170528.1184868-7-philmd@redhat.com>