soc/amd/common/gpio: Add new helper macro PAD_CFG_STRUCT_FLAGS

soc/amd/common/gpio: Add new helper macro PAD_CFG_STRUCT_FLAGS

`flags` field of soc_amd_gpio structure is set only for SCI and SMI
configurations. This change adds a new helper macro
PAD_CFG_STRUCT_FLAGS that allows setting of all soc_amd_gpio members
including `flags` field. This can be used directly by PAD_SCI and
PAD_SMI. For all other pad configurations, PAD_CFG_STRUCT macro uses
PAD_CFG_STRUCT_FLAGS with flags set to 0. This allows dropping of
redundant parameter 0 for flags for all other pad configurations.

BUG=b:159944426

Change-Id: I835b62f5502375ffc4215548b51338a67546d699
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42876
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>