arch/x86/acpigen: Add support for interacting with GPIOs

Since reading/toggling of GPIOs is platform-dependent task, provide an
interface with common functions to generate ACPI AML code for
manipulating GPIOs:
1. acpigen_soc_read_rx_gpio
2. acpigen_soc_get_tx_gpio
3. acpigen_soc_set_tx_gpio
4. acpigen_soc_clear_tx_gpio

Provide weak implementations of above functions. These functions are
expected to be implemented by every SoC that uses ACPI. This allows
drivers to easily generate ACPI AML code to interact GPIOs.

BUG=chrome-os-partner:55988

Change-Id: I3564f15a1cb50e6ca6132638447529648589aa0e
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/17080
Tested-by: build bot (Jenkins)
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
2 files changed