ASoC: SOF: amd: Move signed_fw_image to struct acp_quirk_entry

ASoC: SOF: amd: Move signed_fw_image to struct acp_quirk_entry

The signed_fw_image member of struct sof_amd_acp_desc is used to enable
signed firmware support in the driver via the acp_sof_quirk_table.

In preparation to support additional use cases of the quirk table (i.e.
adding new flags), move signed_fw_image to a new struct acp_quirk_entry
and update all references to it accordingly.

No functional changes intended.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://msgid.link/r/20240220201623.438944-2-cristian.ciocaltea@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>