Fix lsm303agr_mag_driver.c bug
Fix lsm303agr_mag_driver.c bug

1. fix Fix lsm303agr_mag_driver.c bug in drivers/lsm303agr

196510921/STM32_Platform,JUMA-IO/STM32_Platform,cannonrobot/Balance_Car_STM32,JUMA-IO/STM32_Platform,196510921/STM32_Platform,cannonrobot/Balance_Car_STM32,cannonrobot/Balance_Car_STM32,JUMA-IO/STM32_Platform