amd/amd8111: Move HAVE_HARD_RESET to southbridge

amd/amd8111: Move HAVE_HARD_RESET to southbridge

No in-tree amd8111-using board has it not selected, so move
selection from boards to southbridge.

Change-Id: Iabbaa4cd2fd367ed6decec7ef5cdcbae3b264d52
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/654
Reviewed-by: Marc Jones <marcj303@gmail.com>
Tested-by: build bot (Jenkins)