iio: accel: sca3000: replace usages of internal read data helpers by spi helpers

Remove sca3000_read_data_short() function, replacing it by spi_w8r8()
and spi_w8r16be() helpers.

This is an old driver that was not making full use of the newer
infrastructure.

Signed-off-by: Andrew Ijano <andrew.lopes@alumni.usp.br>
Co-developed-by: Gustavo Bastos <gustavobastos@usp.br>
Signed-off-by: Gustavo Bastos <gustavobastos@usp.br>
Suggested-by: Jonathan Cameron <jic23@kernel.org>
Link: https://patch.msgid.link/20250618031638.26477-2-andrew.lopes@alumni.usp.br
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: AndrewIjano