staging: iio: tsl2x7x: remove unnecessary code

staging: iio: tsl2x7x: remove unnecessary code

As a follow up to the work in commit a0722d05a195 ("staging: iio:
tsl2x7x: convert mutex_trylock() to mutex_lock()"), this patch removes
the unnecessary calls to tsl2x7x_get_prox() and tsl2x7x_get_lux() in
tsl2x7x_event_handler(). Previously, these functions were locked with
mutex_trylock(), but that is no longer the case. This patch also removes
a comment that is no longer relevant about returning the last sample.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>