reset: Finalize move to new API

Move soft_reset() to `southbridge/amd/common/` it's only used for
amdfam10 now.

Drop hard_reset() for good.

Change-Id: Ifdc5791160653c5578007f6c1b96015efe2b3e1e
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/29059
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/security/vboot/Kconfig

@@ -18,7 +18,7 @@ config VBOOT
 	bool "Verify firmware with vboot."
 	default n
 	select VBOOT_MOCK_SECDATA if !TPM1 && !TPM2
-	depends on HAVE_HARD_RESET || !MISSING_BOARD_RESET
+	depends on !MISSING_BOARD_RESET
 	help
 	  Enabling VBOOT will use vboot to verify the components of the firmware
 	  (stages, payload, etc).