CH32v3x: Doc update, precision on flash programming

[mean00]

Hi,
1- There is a small typo in the CH32V2/3 v1.7 ref manual. In 32.5.6, for CH32V3x the page size is 256 bytes not 128. Later on it says 64*4 bytes = 256

2- The way the flash programming is explained is a bit confusing. It says

Use 32-bit mode to write data to the FLASH address, for example
    *(uint32_t*)0x80000000 = 0x12345678;

which makes sense for a CH32F103 or similar chip where the flash is at an address which starts at 0x08000000.
But there is an extra zero.

I think what it actually meant is you have to make sure bit 31 is set
i.e. it could be reworded to

Use 32-bit mode to write data to the FLASH address with the bit 31 set, for example
 *(uint32_t *)( (1<<31) |0x1000)=0x12345678 
to write at flash address 0x1000

Thank you!

[qiyongshuang]

Thanks for your finding ,we will fix it in next version.
1.CH32V3x the page size is 256 bytes
2.Use 32-bit mode to write data to the FLASH address, for example
(uint32_t)0x80000000 = 0x12345678;
there is an extra zero.