usb: typec: tipd: declare in_data in as const in exec_cmd functions

The input data passed to execute commands with tps6598x_exec_cmd()
is not supposed to be modified by the function. Moreover, this data is
passed to tps6598x_exec_cmd_tmo() and finally to tps6598x_block_write(),
which expects a const pointer.

The current implementation does not produce any bugs, but it discards
const qualifiers from the pointers passed as arguments. This leads to
compile issues if 'discarded-qualifiers' is active and a const pointer
is passed to the function, which is the case if data from a firmware
structure is passed to execute update commands. Adding the const
modifier to in_data prevents such issues and provides code consistency.

Signed-off-by: Javier Carrasco <javier.carrasco@wolfvision.net>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20231207-tps6598x_update-v2-3-f3cfcde6d890@wolfvision.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>