soc/intel/apollolake: Remove set_subsystem() from SoC

Intel common PCI driver is handle PCI subsystem ID
programming, hence no need to have an explicit soc
function to do the same.

TEST=PCI subsystem id is getting programming during
pci enumeration.

Change-Id: I3eb362ff1f3f6d5c81a0dbe854d8ecd59d5a0453
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/22770
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/soc/intel/apollolake/chip.h

@@ -148,6 +148,5 @@ struct soc_intel_apollolake_config {
 };
 
 typedef struct soc_intel_apollolake_config config_t;
-extern struct pci_operations soc_pci_ops;
 
 #endif	/* _SOC_APOLLOLAKE_CHIP_H_ */