Can not guess flash more than 16MB correctly

[zx-wowuying]

I designed a development board with two 16M flash chips and correctly configured the opt parameters, but picotool can only recognize 16M of space.I found an issue in the source code of guess_flash_size

    // Read at decreasing power-of-two addresses until we don't see the boot pages again
    const int min_size = 16 * PAGE_SIZE;
    const int max_size = 8 * 1024 * 1024;
    int size;
    for (size = max_size; size >= min_size; size >>= 1) {
        auto new_pages = access.read_vector<uint8_t>(FLASH_START + size, 2 * PAGE_SIZE);
        if (!std::equal(first_two_pages.begin(), first_two_pages.end(), new_pages.begin())) break;
    }
    return size * 2;

Then I change the max_size to 16x1024x1024，All the picotool functions,such as info /load/save .. can run correctly.
Considering future scalability, there should be a better configuration option to address this issue.

[will-v-pi]

This won't work correctly if you had, for example, an 16M and an 8M flash chip connected, or an 8M flash and an 8M PSRAM chip connected - this fuction can only correctly guess the flash size for a single chip select window.

You'll have to load files separately into CS0 and CS1 windows, which was fixed with #121 - this should make it possible to use picotool save --range 0x11000000 0x12000000 cs1.bin to save the data from the second flash chip, and picotool load --offset 0x11000000 cs1.bin to load files into the second flash chip.