gpio: Add Aspeed SGPIO driver

The Aspeed SGPIO driver supports the SGPIO controllers found in the
AST2400, AST2500 and AST2600 BMC SoCs. The implementation is a cut-down
copy of the upstream Linux kernel driver, adapted for u-boot.

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
3 files changed