drivers: i2c: fixup comments outlining command arguments
drivers: i2c: fixup comments outlining command arguments

Some comments were missing, and others were misleading. This is now
resolved.

Signed-off-by: Attie Grande <1e84f2a626694e9841f0d16b88e7db2a21db91f2@argentum-systems.co.uk>

galak/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr