iio: mraa_iio_write_string now using open insteam of fopen
iio: mraa_iio_write_string now using open insteam of fopen

Signed-off-by: Henry Bruce <57ea958cad66de244404958c9a01f7a4ad51b29e@intel.com>

stefan-andritoiu/mraa-gpio-chardev,Pillar1989/mraa,KurtE/mraa,petreeftime/mraa,stefan-andritoiu/mraa,malikabhi05/mraa,sergev/mraa,ProfFan/mraa,ncrastanaren/mraa,arunlee77/mraa,anonymouse64/mraa,Propanu/mraa,w4ilun/mraa,KurtE/mraa,arunlee77/mraa,petreeftime/mraa,Propanu/mraa,Hbrinj/mraa,Propanu/mraa,Hbrinj/mraa,spitfire88/mraa,petreeftime/mraa,sergev/mraa,anonymouse64/mraa,intel-iot-devkit/mraa,intel-iot-devkit/mraa,ncrastanaren/mraa,spitfire88/mraa,andreivasiliu2211/mraa,spitfire88/mraa,ProfFan/mraa,sergev/mraa,whbruce/mraa,ncrastanaren/mraa,andreivasiliu2211/mraa,andreivasiliu2211/mraa,ncrastanaren/mraa,arfoll/mraa,stefan-andritoiu/mraa,arfoll/mraa,stefan-andritoiu/mraa,malikabhi05/mraa,whbruce/mraa,KurtE/mraa,KurtE/mraa,jontrulson/mraa,Jon-ICS/mraa,alext-mkrs/mraa,malikabhi05/mraa,andreivasiliu2211/mraa,g-vidal/mraa,stefan-andritoiu/mraa-gpio-chardev,alext-mkrs/mraa,Jon-ICS/mraa,g-vidal/mraa,stefan-andritoiu/mraa-gpio-chardev,malikabhi05/mraa,ProfFan/mraa,ProfFan/mraa,intel-iot-devkit/mraa,Hbrinj/mraa,intel-iot-devkit/mraa,jontrulson/mraa,yongli3/mraa,sergev/mraa,arfoll/mraa,g-vidal/mraa,arfoll/mraa,arfoll/mraa,spitfire88/mraa,w4ilun/mraa,arunlee77/mraa,stefan-andritoiu/mraa,yongli3/mraa,stefan-andritoiu/mraa,jontrulson/mraa,malikabhi05/mraa,yongli3/mraa,ncrastanaren/mraa,alext-mkrs/mraa,yongli3/mraa,petreeftime/mraa,Propanu/mraa,whbruce/mraa,g-vidal/mraa,Pillar1989/mraa,g-vidal/mraa,arunlee77/mraa,jontrulson/mraa,Pillar1989/mraa,Propanu/mraa,yongli3/mraa,jontrulson/mraa,Hbrinj/mraa,alext-mkrs/mraa,KurtE/mraa,intel-iot-devkit/mraa,whbruce/mraa,stefan-andritoiu/mraa-gpio-chardev,w4ilun/mraa,stefan-andritoiu/mraa-gpio-chardev,anonymouse64/mraa,w4ilun/mraa,Jon-ICS/mraa,alext-mkrs/mraa,sergev/mraa