iio: mxs-lradc: indexes are unsigned
iio: mxs-lradc: indexes are unsigned

Fix the following warning when building with W=1 option:

drivers/staging/iio/adc/mxs-lradc.c: In function 'mxs_lradc_trigger_handler':
drivers/staging/iio/adc/mxs-lradc.c:244:2: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

Signed-off-by: Fabio Estevam <679188261afeb60eb822cd934fd7b46a48ddd743@freescale.com>
Acked-by: Marek Vasut <f40600653b33f5282fa4c5daf377dfc444fb4625@denx.de>
Signed-off-by: Jonathan Cameron <09f65b71b7655725897b2fd41a09a0cefe2e1ace@kernel.org>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas