i3c: Remove the const qualifier from i2c_msg pointer in i2c_xfers API

The change is necessary to enable the use of the
`i2c_get_dma_safe_msg_buf()` API, which requires a non-const
`struct i2c_msg *` to operate. The `i2c_get_dma_safe_msg_buf()` function
ensures safe handling of I2C messages when using DMA, making it essential
for scenarios where DMA transfers are involved. By removing the `const`
qualifier, this patch allows drivers to prepare and manage DMA-safe
buffers directly.

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
Link: https://lore.kernel.org/r/20250204091702.4014466-1-billy_tsai@aspeedtech.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>