wifi: rtw89: pci: add group BD address design

wifi: rtw89: pci: add group BD address design

The newly designed group BD address is to use the same starting DMA address
with offset as below picture:

 Original            DMA memory         Group BD address

 +--------+  (*1)   +---------+   (*2)  +--------+
 |  CH 0 -|-------> |         | <-------|- CH 0  | <-+--+--+--+
 +--------+         |         |         |        |   |  |  |  |
 |  CH 1 -|-------> |         |         |  CH 1 -|---+  |  |  |
 +--------+         |         |         |        |      |  |  |
 |  CH 2 -|-------> |         |         |  CH 2 -|------+  |  |
 +--------+         |         |         |        |         |  |
 |  CH 3 -|-------> |         |         |  CH 3 -|---------+  |
 +--------+         |         |         |        |            |
 |    :  -|-------> |         |         |    :  -|------------+
 +--------+         |         |         +--------+   (*3; offset from CH 0)
 |  CH 8 -|-------> |         | <-------|- CH 8  | <-+
 +--------+         |         |         |        |   | (offset from CH 8)
 |    :  -|-------> |         |         |    :  -|---+
 +--------+         +---------+         +--------+

Compare (*1) and (*2), for original design, each DMA channel has
individual DMA address, so it is not necessary to allocate continual
DMA address across channels. For group BD address, only two DMA address
are set, and each channel set the offset (*3) from base address.

The element number and offset of a channel are encoded rather than a
raw number, so add a function to translate numbers into hardware format.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250826085318.28361-1-pkshih@realtek.com