spi: dw: Convert to using BITS_TO_BYTES() macro

Since commit dd3e7cba ("ocfs2/dlm: move BITS_TO_BYTES() to bitops.h
for wider use") there is a generic helper available to calculate a number
of bytes needed to accommodate the specified number of bits. Let's use it
instead of the hard-coded DIV_ROUND_UP() macro function.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20240424150657.9678-2-fancer.lancer@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>