spi: Use FIELD_MODIFY() for bitfield operations

Hans Zhang <18255117159@163.com> says:

Replace open-coded bitfield modifications with the standard FIELD_MODIFY()
macro across multiple SPI controller drivers. This improves readability and
adds compile-time checking without functional changes.

Each patch modifies a single driver, allowing independent review and
application.

Link: https://patch.msgid.link/20260430155456.36998-1-18255117159@163.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --cc drivers/spi/spi-amlogic-spisg.c
Simple merge

diff --cc drivers/spi/spi-meson-spicc.c
Simple merge

diff --cc drivers/spi/spi-uniphier.c
Simple merge