iio: ti_am335x_adc: Adjust the closing bracket in tiadc_read_raw()

It somehow looks like the ending bracket belongs to the if statement but
it does belong to the while loop. This patch moves the bracket where it
belongs.
Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: NJonathan Cameron <jic23@kernel.org>
Signed-off-by: NLee Jones <lee.jones@linaro.org>