soc/intel/common: don't infinitely recurse in busmaster_disable_on_bus()

If a bridge has the primary bus equal to the secondary bus the
busmaster_disable_on_bus() will infinitely call itself. Avoid the
inifinite recursion by checking current bus number against the
secondary bus number.

BUG=chrome-os-partner:54262
TEST=Ran on reef. Able to actually get the chipset to assert SLP_Sx
     signals which means no more infinite recursion.

Change-Id: I52b21fbba24e6a652ea8f9f87f5f49f60109c8f2
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/15157
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins)
1 file changed