iio: adc: adi-axi-adc: Drop false marking for kernel-doc

This comment block isn't in kernel-doc format so drop the /** marking.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20210314164655.408461-7-jic23@kernel.org

drivers/iio/adc/adi-axi-adc.c

@@ -23,7 +23,7 @@
 #include <linux/fpga/adi-axi-common.h>
 #include <linux/iio/adc/adi-axi-adc.h>
 
-/**
+/*
  * Register definitions:
  *   https://wiki.analog.com/resources/fpga/docs/axi_adc_ip#register_map
  */