i2c: shell: Add help to command description

SHELL_STATIC_SUBCMD_SET_CREATE(sub_i2c_cmds,

	SHELL_CMD_ARG(scan, &dsub_device_name,

					     "Scan I2C devices",

		      "Scan I2C devices\n"

		      "Usage: scan <device>",

		      cmd_i2c_scan, 2, 0),

	SHELL_CMD_ARG(recover, &dsub_device_name,

					     "Recover I2C bus",

		      "Recover I2C bus\n"

		      "Usage: recover <device>",

		      cmd_i2c_recover, 2, 0),

	SHELL_CMD_ARG(read, &dsub_device_name,

					     "Read bytes from an I2C device",

		      "Read bytes from an I2C device\n"

		      "Usage: read <device> <addr> <reg> [<bytes>]",

		      cmd_i2c_read, 4, 1),

	SHELL_CMD_ARG(read_byte, &dsub_device_name,

					     "Read a byte from an I2C device",

					     cmd_i2c_read_byte, 4, 1),

		      "Read a byte from an I2C device\n"

		      "Usage: read_byte <device> <addr> <reg>",

		      cmd_i2c_read_byte, 4, 0),

	SHELL_CMD_ARG(write, &dsub_device_name,

					     "Write bytes to an I2C device",

		      "Write bytes to an I2C device\n"

		      "Usage: write <device> <addr> <reg> [<byte1>, ...]",

		      cmd_i2c_write, 4, MAX_I2C_BYTES),

	SHELL_CMD_ARG(write_byte, &dsub_device_name,

					     "Write a byte to an I2C device",

		      "Write a byte to an I2C device\n"

		      "Usage: write_byte <device> <addr> <reg> <value>",

		      cmd_i2c_write_byte, 5, 0),

	SHELL_SUBCMD_SET_END     /* Array terminated. */

);