wifi: brcmfmac: fix scatter-gather handling by detecting end of sg list

The scatter-gather handling uses a pre-allocated list (with nents entries).
If the driver runs out of sg entries it will result in an oops. Let's detect
this instead and make the SDIO block transfer fail.

Signed-off-by: Norbert van Bolhuis <nvbolhuis@gmail.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://patch.msgid.link/20241108125609.107016-1-nvbolhuis@gmail.com