staging: iio: accel: Rename source files and update Makefile

Rename adis162xx_core.c files to adis162xx.c because
these are the only source files for these drivers.

Update Makefile to correspond to the new file names.

Signed-off-by: Narcisa Ana Maria Vasile <[e-mail]>

rename drivers/staging/iio/accel/{adis16201_core.c => adis16201.c} (100%)
rename drivers/staging/iio/accel/{adis16203_core.c => adis16203.c} (100%)
rename drivers/staging/iio/accel/{adis16209_core.c => adis16209.c} (100%)
rename drivers/staging/iio/accel/{adis16240_core.c => adis16240.c} (100%)
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/staging/iio/accel/Makefile

···
 # Makefile for industrial I/O accelerometer drivers
 #
 
-adis16201-y             := adis16201_core.o
 obj-$(CONFIG_ADIS16201) += adis16201.o
-
-adis16203-y             := adis16203_core.o
 obj-$(CONFIG_ADIS16203) += adis16203.o
-
-adis16209-y             := adis16209_core.o
 obj-$(CONFIG_ADIS16209) += adis16209.o
-
-adis16240-y             := adis16240_core.o
 obj-$(CONFIG_ADIS16240) += adis16240.o