CVE-2026-31768

In the Linux kernel, the following vulnerability has been resolved:

iio: adc: ti-adc161s626: use DMA-safe memory for spi_read()

Add a DMA-safe buffer and use it for spi_read() instead of a stack
memory. All SPI buffers must be DMA-safe.

Since we only need up to 3 bytes, we just use a u8[] instead of __be16
and __be32 and change the conversion functions appropriately.