amd/sb600: Move HAVE_HARD_RESET to southbridge

No in-tree board using that chipset has it not selected, so move
selection from boards to southbridge.

Change-Id: I16b27e40ca1a201b2f968f8ce303eaafe43804c0
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/660
Tested-by: build bot (Jenkins)

src/southbridge/amd/sb600/Kconfig

@@ -21,6 +21,7 @@ config SOUTHBRIDGE_AMD_SB600
 	bool
 	select IOAPIC
 	select HAVE_USBDEBUG
+	select HAVE_HARD_RESET
 
 if SOUTHBRIDGE_AMD_SB600
 config BOOTBLOCK_SOUTHBRIDGE_INIT