mce, amd: Implement mce_threshold_block_init() helper function

This patch adds a helper function for the initial setup of an
mce threshold block. The LVT offset is passed as argument. Also
making variable threshold_defaults local as it is only used in
function mce_amd_feature_init(). Function
threshold_restart_bank() is extended to setup the LVT offset,
the change is backward compatible. Thus, now there is only a
single wrmsrl() to setup the block.

Signed-off-by: Robert Richter <robert.richter@amd.com>
Acked-by: Borislav Petkov <borislav.petkov@amd.com>
LKML-Reference: <1288015419-29543-2-git-send-email-robert.richter@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>