Add flag boot_time_tmr to indicate boot time TMR or runtime TMR
instead of function.

v2: rework logic (Alex)

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>