mfd: tps6594: Add driver for TI TPS6594 PMIC

This patch adds support for TPS6594 PMIC MFD core. It provides
communication through the I2C and SPI interfaces, and supports
protocols with embedded CRC data fields for safety applications.

Signed-off-by: Julien Panis <jpanis@baylibre.com>
Link: https://lore.kernel.org/r/20230511095126.105104-3-jpanis@baylibre.com
Signed-off-by: Lee Jones <lee@kernel.org>